Method, apparatus, system, and program for code conversion transmission and code conversion reception of audio data

ABSTRACT

A system and a method of suppressing outstanding degradation of decoded audio quality due to a transmission error of audio coded data are provided without feedback information from a receiver, thereby reducing the increase of the number of necessary transmission bands and the arithmetic complexity on the receiving side. A code conversion and transmission apparatus  100  for inputting audio coded data includes first to N-th code conversion and transmission units  102  and  104  to  106  for converting audio data to N pieces of coded data, and transmitting the data at predetermined or adaptively variable time intervals to M transmission lines  130 . The second to N-th audio code conversion and transmission units  104  to  106  codes a frame at a compression rate equal to or higher than the rate of input coded data. The code conversion and reception apparatus  120  selects a transmission line using a selection unit  107 , and selecting data from correctly received coded data in a frame or packet unit, thereby reconfiguring the coded data using a coded data reconfiguration unit  112.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a divisional application of application Ser.No. 10/512,648 filed on Oct. 25, 2004.

TECHNICAL FIELD

The present invention relates to an audio coded data transmissiontechnology, and more specifically to a code conversion and transmissionmethod for transmitting audio coded data, a code conversion andreception method for receiving coded and converted audio data, a system,an audio code conversion and transmission apparatus and a codeconversion and reception apparatus, and a program executed by a computerfor performing audio code conversion and transmission/audio codeconversion and reception processes.

BACKGROUND ART

Recently, a method for transmitting high-efficiency compression codeddata based on a modified discrete cosine transform (MDCT) has beenwidely used as a method for efficiently transmitting audio data. In thismethod, an audio signal is divided into frames, the MDCT is performed onthe frames, the number of quantization bits are assigned to an MDCTcoefficient based on a psychological audio model, the MDCT coefficientis quantized and transmitted. Thus, audio data can be transmitted usinga small number of transmission bands by efficiently compressing andcoding data.

A typical example is the MPEG (Moving Picture Expert Group)-4 AAC(Advanced Audio Coding), etc.

PROBLEMS THAT THE INVENTION IS TO SOLVE

However, in the conventional audio transmitting method, when atransmitted data error having long burst or a loss of a transmittedpacket which are irrecoverable even by using an error-correcting codeoccurs, a receiver cannot correctly decode the audio data in the framein which an error has occurred. A countermeasure of the receiver can bean error concealment method in which an error is replaced with an audiosignal in a past frame for which data has been correctly decoded.However, in this case, the degradation of the sound quality cannot beavoided. When a coding efficiency is enhanced through intra-frameprediction of an MDCT coefficient, there occurs the problem that oncearising degradation is propagated to the subsequent frames.

In the multicast/broadcast information distribution, a receiver cannottransmit to a transmitter the information about an error of transmitteddata or a loss of a transmitted packet. When a receiver feeds back errorinformation to a transmitter, the bands are occupied by the feedbackinformation.

The present invention has been developed to solve the above-mentionedproblems, and first aims at providing an audio data code conversion andtransmission method, reception method, apparatus, system, and programcapable of suppressing the outstanding degradation of a decoded audiosignal caused by a transmission error of audio coded data and receivedby the receiver down to an audibly tolerable level.

The present invention second aims at providing an audio data codeconversion and transmission method, reception method, apparatus, system,and program allowing a user to set the trade-off of the transmissionband available in the transmission of audio data and audio quality.

The present invention third aims at providing an audio data codeconversion and transmission method, reception method, apparatus, system,and program capable of preventing an increase in the arithmeticcomplexity required in decoding compressed audio coded data.

The present invention fourth aims at providing a method, apparatus,system, and program for attaining the first objective withouttransmitting the feedback information from a receiver to a transmitter.

DISCLOSURE OF THE INVENTION

The apparatus according to the present invention which solves at leastone of the above-mentioned objectives is a code conversion andtransmission apparatus which inputs audio coded data, converts it andoutputs it to a transmission line. The apparatus includes a plurality ofaudio code conversion and transmission means for outputting a stream ofthe input audio coded data and a stream of audio coded data obtained bydecoding and recoding the input audio coded data, or outputting pluralpieces of audio coded data obtained by recoding the data obtained bydecoding the input audio coded data. The plurality of audio codeconversion and transmission means outputs all or a selected part ofaudio coded data and/or the recoded audio coded data, and the pluralityof audio coded data from the plurality of audio code conversion andtransmission means are output to one or more transmission lines. In thepresent invention, the code conversion and reception apparatus whichreceives audio coded data transmitted from the code conversion andtransmission apparatus to the transmission line includes means forselecting a transmission line for receiving data from the one or moretransmission lines, and means for receiving audio coded data from theselected transmission line, and reconfiguring audio coded data based oncorrectly received coded data.

The code conversion and transmission apparatus according to one aspectof the present invention includes:

(a) first audio code conversion and transmission means for inputtingcompressed audio coded data, and outputting all or a part of frames ofthe input audio coded data;

(b) second to N-th (N is a predetermined integer equal to or larger than2) audio code conversion and transmission means for decoding all or apart of input audio coded data, coding data obtained by decoding data,and outputting all or a part of frames of obtained coded data; and

(c) means for transmitting output of the first to N-th audio codeconversion and transmission means to first to M-th (M is a predeterminedinteger equal to or larger than 1) transmission lines.

The code conversion and transmission apparatus according to anotheraspect of the present invention includes:

(a) first audio code conversion and transmission means for inputtingcompressed audio coded packet data and outputting all or a part ofpackets of the input audio coded data;

(b) second to N-th (N is a predetermined integer equal to or larger than2) audio code conversion and transmission means for decoding the inputaudio coded packet data, coding data obtained by decoding data, andoutputting all or a part of obtained packet data; and

(c) means for transmitting output of the first to N-th audio codeconversion and transmission means to first to M-th (M is a predeterminedinteger equal to or larger than 1) transmission lines.

The code conversion and reception apparatus according to another aspectof the present invention includes:

(e) selection means for selecting a transmission line for receivingcoded data from first to M-th (M is a predetermined integer equal to orlarger than 1) transmission lines; and

(f) means for receiving coded data from the transmission line selectedby the selection means, extracting coded data received without atransmission error or a loss, reconfiguring coded data based on theextracted coded data and outputting the result.

The code conversion and reception apparatus according to another aspectof the present invention includes:

(e) selection means for selecting a transmission line for receivingcoded data from first to M-th (M is a predetermined integer equal to orlarger than 1) transmission lines; and

(f) means for receiving coded data from the transmission line selectedby the selection means, extracting coded packet data received without atransmission error or a loss, reconfiguring coded packet data based onthe extracted coded packet data, and outputting the result.

The code conversion and transmission method according to another aspectof the present invention includes:

(a) a step of first audio code conversion and transmission meansinputting compressed audio coded data, and outputting all frames (orpackets) or a part of frames (or packets) of the input audio coded data;

(b) a step of second to N-th (N is a predetermined integer equal to orlarger than 2) audio code conversion and transmission means decoding allor a part of input audio coded data, coding data obtained by decodingdata, and outputting all frames (or packets) or a part of frames (orpackets) of the obtained coded data; and

(c) a step of transmitting output of the first to N-th audio codeconversion and transmission means to first to M-th (M is a predeterminedinteger equal to or larger than 1) transmission lines.

The code conversion and reception method according to another aspect ofthe present invention includes:

(d) a step of selecting a transmission line for receiving audio codeddata from first to M-th (M is a predetermined integer equal to or largerthan 1) transmission lines; and

(e) a step of receiving coded data from the selected transmission line,extracting audio coded data (packet) received without an transmissionerror and a loss, reconfiguring audio coded data based on the extractedcoded data (packet data), and outputting the result.

The computer program according to another aspect of the presentinvention used to direct a computer forming part of the audio data codeconversion and transmission apparatus and having first audio codeconversion and transmission means and second to N-th (N is apredetermined integer equal to or larger than 2) audio code conversionand transmission means, to perform a code conversion and transmissionprocess on audio coded data, includes:

(a) a process of first audio code conversion and transmission meansinputting compressed audio coded data, and outputting all frames or apart of frames of the input audio coded data;

(b) a process of second to N-th (N is a predetermined integer equal toor larger than 2) audio code conversion and transmission means decodingall or a part of input audio coded data, coding data obtained bydecoding data, and outputting all frames or a part of frames of theobtained coded data; and

(c) a process of transmitting output of the first to N-th audio codeconversion and transmission means to first to M-th (M is a predeterminedinteger equal to or larger than 1) transmission lines.

The computer program according to another aspect of the presentinvention is used to direct a computer forming part of the audio datacode conversion and reception apparatus to perform the code conversionprocess on audio coded data including:

(d) a process of selecting at least one transmission line from M ((M isa predetermined integer equal to or larger than 1) transmission lines;

(e) a process of receiving audio coded data from the selectedtransmission line, extracting coded data (packet data) received withouta transmission error and a loss, reconfiguring audio coded data based onthe extracted coded data (packet data), and outputting the result.

SUMMARY OF THE INVENTION

In the present invention, to prevent the audio quality from beingexceedingly degraded by a transmission error of compressed audio codeddata, the code conversion and transmission apparatus receives coded datafrom the audio coding apparatus, converts data into a format forprotection of data against a loss or an error in a transmission line,and transmits data to the code conversion and reception apparatus.

In the present invention, the code conversion and transmission apparatusincludes the first to N-th audio code conversion and transmission meansand transmission means to the first to N-th transmission lines,compresses and codes the audio data into N pieces of coded data, andtransmits the data. The code conversion and reception apparatus selectscoded data having the lowest compression rate and a higher audio qualitylevel in the coded data correctly received from M transmission lines,and decodes the selected data.

In the present invention, the N pieces of coded data obtained by thefirst to N-th audio code conversion and transmission means aretransmitted by being arranged at predetermined or adaptively variabletime intervals.

In the present invention, the code conversion and reception apparatusselects coded data having the lowest compression rate and a higher audioquality from correctly received coded data in a frame or packet unitfrom at least one transmission line in M pieces of transmission lines,and decodes the selected data.

Additionally, according to the present invention, the compression ratefor the first to N-th audio code conversion and transmission means canbe selected depending on the transmission band available in the first toM-th transmission lines. The second to N-th audio code conversion andtransmission means can code data at a compression rate equal to orhigher than the rate of the first audio code conversion and transmissionmeans, or can arbitrarily set the rate.

In the present invention, to prevent the arithmetic complexity fromincreasing on the receiving side in transmitting plural pieces of codeddata, the code conversion and transmission apparatus generates the sameframe of coded data, and the receiver selects at least one frame orpacket of data from the received plural pieces of coded data, anddecodes the selected data.

To be more practical, in the audio data conversion and transmissionsystem according to the first aspect of the present invention, the codeconversion and transmission apparatus includes for an integer N of 2 orlarger and an integer M of 1 or larger: a) first audio code conversionand transmission means for inputting compressed coded data, andtransmitting all frames or a part of frames adaptively selecteddepending on the characteristics of input audio data or according to apredetermined rule using predetermined transmission means; b) (N−1)units of the second to N-th audio code conversion and transmission meansfor decoding input coded data, compressing and coding data at acompression rate equal to or higher than the rate of the first audiocode conversion and transmission means, and transmitting all frames ofobtained coded data or a part of frames adaptively selected depending onthe characteristic of input audio data or according to a predeterminedrule at predetermined or adaptively variable time intervals usingtransmission means the same as or different from the transmission meansof the first audio code conversion and transmission means; and c) meansfor selecting a compression rate for coding of at least one of the firstto N-th audio code conversion and transmission means depending on theband available for each of the first to M-th transmission lines, andtransmitting it to the first to M-th transmission lines.

The code conversion and reception apparatus includes d) selection meansfor selecting at least one transmission line from M transmission lines,receiving N pieces of coded data from the selected transmission line,extracting coded data received without a transmission error or a loss,selecting audio coded data from the coded data in the same frame basedon a compression rate, and outputting the selected data.

In the audio data conversion and transmission system according to thesecond aspect of the present invention, the code conversion andtransmission apparatus includes for an integer N of 2 or larger and aninteger M of 1 or larger: a) first audio code conversion andtransmission means for inputting compressed coded packet data, andtransmitting all packets or a part of packets adaptively selecteddepending on the characteristics of input audio data or according to apredetermined rule using predetermined transmission means; b) (N−1)units of the second to N-th audio code conversion and transmission meansfor decoding input coded packet data, compressing and coding data intopacket data at a compression rate equal to or higher than the rate ofthe first audio code conversion and transmission means, and transmittingall obtained packet data or packet data adaptively selected depending onthe characteristic of input audio data or according to a predeterminedrule at predetermined or adaptively variable time intervals usingtransmission means the same as or different from the transmission meansof the first audio code conversion and transmission means; and c) meansfor selecting a compression rate for coding of at least one of the firstto N-th audio code conversion and transmission means depending on theband available for each of the first to M-th transmission lines, andtransmitting it to the first to M-th transmission lines.

The code conversion and reception apparatus includes selection means forselecting at least one transmission line from M transmission lines,receiving up to N pieces of coded data from the selected transmissionline, selecting coded packet data received without a transmission erroror a loss from the packet data in the same frame based on a compressionrate, and outputting the selected data.

In the audio data conversion and transmission system according to thethird aspect of the present invention, the code conversion andtransmission apparatus includes, for an integer N of 2 or larger and aninteger M of 1 or larger: d) first audio code conversion andtransmission means for inputting compressed coded data, compressing andcoding all frames of decoded audio data or a part of frames selecteddepending on the characteristic of input audio data or according to apredetermined rule at a compression rate equal to or higher than therate of the input audio data, and transmitting obtained coded data usingpredetermined transmission means; e) (N−1) units of the second to N-thaudio code conversion and transmission means for coding all frames codedby the first audio code conversion and transmission means or a part offrames adaptively selected depending on the characteristic of inputaudio data or according to a predetermined rule at a compression rateequal to or higher than the rate of the first audio code conversion andtransmission means, and transmitting obtained coded data atpredetermined or adaptively variable time intervals using transmissionmeans the same as or different from the transmission means of the firstaudio code conversion and transmission means; and f) means for selectinga compression rate for coding for at least one of the first to N-thaudio code conversion and transmission means depending on the bandavailable for each of the first to M-th transmission lines, andtransmitting it to the first to M-th transmission lines.

The code conversion and reception apparatus includes g) selection meansfor selecting at least one transmission line from M transmission lines,receiving N pieces of coded data from the selected transmission line,extracting coded data received without a transmission error or a loss,selecting audio coded data from the coded data in the same frame basedon a compression rate, and outputting the selected data.

In the audio data conversion and transmission system according to thefourth aspect of the present invention, the code conversion andtransmission apparatus includes for an integer N of 2 or larger and aninteger M of 1 or larger: a) first audio code conversion andtransmission means for decoding input coded packet data, compressing andcoding the data at a compression rate equal to or higher than the rateof the input audio data, and transmitting the obtained one or morepieces of coded packet data using predetermined transmission means; b)(N−1) units of the second to N-th audio code conversion and transmissionmeans for coding all packet data coded by the audio code conversion andtransmission means or packet data adaptively selected depending on thecharacteristic of input audio data or according to a predetermined ruleinto packet data at a compression rate equal to or higher than the rateof the first audio code conversion and transmission means, andtransmitting the obtained coded packet data at predetermined oradaptively variable time intervals using transmission means the same asor different from the transmission means of the first audio codeconversion and transmission means; and c) means for selecting acompression rate for coding for at least one of the first to N-th audiocode conversion and transmission means depending on the band availablefor the first to M-th transmission line, and transmitting it to thefirst to M-th transmission lines.

The code conversion and reception apparatus includes d) selection meansfor selecting at least one transmission line from M transmission lines,receiving N pieces of coded data from the selected transmission line,selecting coded packet data which has the lowest compression rate fromthe packet data of the same frame received without a transmission erroror a loss, and outputting the selected data.

In the audio data conversion and transmission system according to thefifth aspect of the present invention, the code conversion andtransmission apparatus includes for an integer N of 2 or larger and aninteger M of 1 or larger: a) first audio code conversion andtransmission means for inputting coded packet data and transmitting allor a part of the frames/packets using predetermined transmission means;b) (N−1) units of the second to N-th audio code conversion andtransmission means for replicating packets for all packet data coded bythe first audio coding means or packet data adaptively selecteddepending on the characteristic of input audio data or according to apredetermined rule, and transmitting the obtained packet data atpredetermined or adaptively variable time intervals using transmissionmeans the same as or different from the transmission means of the firstaudio code conversion and transmission means; and c) means fortransmitting output of the first to N-th audio code conversion andtransmission means to the first to M-th transmission lines.

The code conversion and reception apparatus includes d) selection meansfor selecting at least one transmission line from M transmission lines,receiving N pieces of coded data from the selected transmission line,selecting coded packet data which is received without a transmissionerror or a loss from the packet data of the same frame, and outputtingthe selected data.

In the audio data conversion and transmission system according to thesixth aspect of the present invention, the code conversion andtransmission apparatus includes for an integer N of 2 or larger and aninteger M of 1 or larger: a) first audio code conversion andtransmission means for inputting compressed coded data, decoding theinput coded data, compressing and coding the data at a compression rateequal to or higher than the rate of the input coded data, andtransmitting all frames or a frame adaptively selected depending on thecharacteristic of input audio data or according to a predetermined ruleusing predetermined transmission means; b) (N−1) units of the second toN-th audio code conversion and transmission means for decoding inputcoded data, compressing and coding data at a compression rate equal toor higher than the rate of the first audio code conversion andtransmission means, and transmitting all frames of the obtained codeddata or a frame adaptively selected depending on the characteristic ofinput audio data or according to a predetermined rule at predeterminedor adaptively variable time intervals using transmission means the sameas or different from the transmission means of the first audio codeconversion and transmission means; and c) means for selecting acompression rate for coding for at least one of the first to N-th audiocode conversion and transmission means depending on the band availablefor each of the first to M transmission lines, and transmitting theselected result to the first to M-th transmission lines.

The code conversion and reception apparatus includes d) selection meansfor selecting at least one transmission line from M transmission lines,receiving N pieces of coded data from the selected transmission line,extracting coded data received without a transmission error or a loss,selecting audio coded data having the lowest compression rate from thecoded data in the same frame, and outputting the selected data.

In the audio data conversion and transmission system according to theseventh aspect of the present invention, the code conversion andtransmission apparatus includes for an integer N of 2 or larger and aninteger M of 1 or larger: a) first audio code conversion andtransmission means for inputting compressed coded packet data, decodingthe input coded packet data, compressing and coding data at acompression rate equal to or higher than the rate of the input codeddata, and transmitting all packets or a packet adaptively selecteddepending on the characteristic of input audio data or according to apredetermined rule using predetermined transmission means; b) (N−1)units of the second to N-th audio code conversion and transmission meansfor decoding input coded packet data, compressing and coding data intopacket data at a compression rate equal to or higher than the rate ofthe first audio code conversion and transmission means; and transmittingall obtained packet data or a part of packet data adaptively selecteddepending on the characteristic of input audio data or according to apredetermined rule at predetermined or adaptively variable timeintervals using transmission means the same as or different from thetransmission means of the first audio code conversion and transmissionmeans; and c) means for selecting a compression rate for coding for atleast one of the first to N-th audio code conversion and transmissionmeans depending on the band available for each of the first to M-thtransmission lines, and transmitting it to the first to M-thtransmission lines.

The code conversion and reception apparatus includes d) selection meansfor selecting at least one transmission line from M transmission lines,receiving N pieces of coded data from the selected transmission line,selecting coded packet data which has the lowest compression rate fromthe packet data of the same frame received without a transmission erroror a loss, and outputting the selected data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the audio data transmission system according to the firstand second embodiments of the present invention.

FIG. 2 shows the configuration of the audio code conversion andtransmission apparatus according to the first and second embodiments ofthe present invention.

FIG. 3 shows the configuration of the code conversion and receptionapparatus according to the first to seventh embodiments of the presentinvention.

FIG. 4 shows the coded data reconfiguring procedure by the audio codeconversion and reception apparatus according to the first embodiment ofthe present invention.

FIG. 5 shows an example of transmitting an audio coded data packetaccording to the first to seventh embodiments of the present invention.

FIG. 6 shows the coded data reconfiguring procedure by the audio codeconversion and reception apparatus according to the second embodiment ofthe present invention.

FIG. 7 shows the configuration of the audio data transmission systemaccording to the third embodiment of the present invention.

FIG. 8 shows the configuration of the audio code conversion andtransmission apparatus according to the third embodiment of the presentinvention.

FIG. 9 shows the coded data reconfiguring procedure by the audio codeconversion and reception apparatus according to the third embodiment ofthe present invention.

FIG. 10 shows the coded data reconfiguring procedure by the audio codeconversion and reception apparatus according to the fourth embodiment ofthe present invention.

FIG. 11 shows the configuration of the audio data code conversion andtransmission system according to the fifth embodiment of the presentinvention.

FIG. 12 shows the configuration of the audio code conversion andtransmission apparatus according to the seventh embodiment of thepresent invention.

FIG. 13 shows the configuration of the audio code converting andtransmitting system according to the sixth and seventh embodiments ofthe present invention.

FIG. 14 shows the configuration of the audio code conversion andtransmission apparatus according to the sixth and seventh embodiments ofthe present invention.

FIG. 15 shows an example of the system configuration according to theeighth embodiment of the present invention.

The reference numeral 10 represents a code conversion and transmissionapparatus. The reference numeral 13 represents a transmission line. Thereference numeral 20 represents a code conversion and receptionapparatus. The reference numeral 30 represents a decoding apparatus. Thereference numeral 40 represents a coding apparatus. The referencenumeral 101 represents an audio data reception unit. The referencenumeral 102 represents a first audio data code conversion andtransmission unit. The reference numeral 103 represents a first audiodata decoding unit. The reference numeral 104 represents a second audiodata code conversion and transmission unit. The reference numeral 105represents a third audio data code conversion and transmission unit. Thereference numeral 106 represents an N-th audio data code conversion andtransmission unit. The reference numeral 107 represents a reception lineselection unit. The reference numeral 100 represents a code conversionand transmission apparatus. The reference numeral 108 represents a firstcoded data reception unit. The reference numeral 109 represents a firstcoded data reception unit. The reference numeral 110 represents a thirdcoded data reception unit. The reference numeral 111 represents an N-thcoded data reception unit. The reference numeral 112 represents a codeddata reconfiguration unit. The reference numeral 120 represents a codeconversion and reception apparatus. The reference numeral 130 representsa transmission line. The reference numeral 200 represents a first audiocode conversion transmission unit. The reference numeral 201 representsa first transmission frame/packet selection unit. The reference numeral202 represents a first error detection code added frame/packetidentification number addition unit. The reference numeral 203represents a decoding unit. The reference numeral 206 represents asecond compression and coding unit. The reference numeral 207 representsa second coded packet generation unit. The reference numeral 208represents a second error detection code added frame/packetidentification number addition unit. The reference numeral 212represents a third compression coding unit. The reference numeral 213represents a third coded packet generation unit. The reference numeral214 represents a third error detection code added frame/packetidentification number addition unit. The reference numeral 220represents a second audio code conversion transmission unit. Thereference numeral 230 represents a third audio code conversiontransmission unit. The reference numeral 300 represents a reception lineselection unit. The reference numeral 301 represents a first packetreception buffer. The reference numeral 302 represents a first codeddata extraction unit. The reference numeral 303 represents a firsterror/packet loss detection unit. The reference numeral 304 represents asecond packet reception buffer. The reference numeral 305 represents asecond coded data extraction unit. The reference numeral 306 representsa second error/packet loss detection unit. The reference numeral 307represents a third packet reception buffer. The reference numeral 308represents a third coded data extraction unit. The reference numeral 309represents a third error/packet loss detection unit. The referencenumeral 310 represents a coded data reconfiguration unit. The referencenumeral 320 represents a first coded data reception unit. The referencenumeral 330 represents a second coded data reception unit. The referencenumeral 340 represents a third coded data reception unit. The referencenumeral 501 represents an audio code conversion apparatus. The referencenumerals 502, 503, 506, and 507 represent delay addition units. Thereference numerals 505 and 509 represent transmission lines. Thereference numeral 510 represents a transmission line selection unit. Thereference numeral 511 represents a separation unit. The referencenumeral 512 represents an audio reception and decoding apparatus. Thereference numeral 700 represents a code conversion and transmissionapparatus. The reference numeral 701 represents an audio data receptionunit. The reference numeral 702 represents an audio data decoding unit.The reference numeral 703 represents a first audio code conversion andtransmission unit. The reference numeral 704 represents a second audiocode conversion and transmission unit. The reference numeral 705represents an N-th audio code conversion and transmission unit. Thereference numeral 706 represents a reception line selection unit. Thereference numeral 707 represents a first coded data reception unit. Thereference numeral 708 represents a second coded data reception unit. Thereference numeral 709 represents an N-th coded data reception unit. Thereference numeral 710 represents a coded data reconfiguration unit. Thereference numeral 720 represents an audio code conversion and receptionapparatus. The reference numeral 730 represents a transmission line. Thereference numeral 800 represents a first audio code conversion andtransmission unit. The reference numeral 801 represents a decoding unit.The reference numeral 804 represents a first compression and codingunit. The reference numeral 805 represents a first coded packetgeneration unit. The reference numeral 806 represents a first errordetection code added frame/packet identification number addition unit.The reference numeral 810 represents a second compression and codingunit. The reference numeral 811 represents a second coded packetgeneration unit. The reference numeral 812 represents a second errordetection code added frame/packet identification number addition unit.The reference numeral 1201 represents an audio data reception unit. Thereference numeral 1202 represents a first audio code conversion andtransmission unit. The reference numeral 1203 represents an audio datareplication unit. The reference numeral 1204 represents a second audiocode conversion and transmission unit. The reference numeral 1205represents an N-th audio code conversion and transmission unit. Thereference numeral 1206 represents a reception line selection unit. Thereference numeral 1207 represents a first coded data reception unit. Thereference numeral 1208 represents a second coded data reception unit.The reference numeral 1209 represents an N-th coded data reception unit.The reference numeral 1210 represents a coded data reconfiguration unit.The reference numeral 1300 represents a first audio code conversion andtransmission unit. The reference numeral 1301 represents a firsttransmitted packets selection unit. The reference numeral 1302represents a first error detection code added frame/packetidentification number addition unit. The reference numeral 1303represents a packet replication unit. The reference numeral 1304represents a second transmitted packets selection unit. The referencenumeral 1305 represents a second error detection code added frame/packetidentification number addition unit. The reference numeral 1310represents a second audio code conversion and transmission unit. Thereference numeral 1401 represents an audio data reception unit. Thereference numeral 1402 represents an audio data decoding unit. Thereference numeral 1403 represents a first audio code conversion andtransmission unit. The reference numeral 1404 represents a second audiocode conversion and transmission unit. The reference numeral 1405represents an N-th audio code conversion and transmission unit. Thereference numeral 1406 represents a reception line selection unit. Thereference numeral 1407 represents a first coded data reception unit. Thereference numeral 1408 represents a second coded data reception unit.The reference numeral 1409 represents an N-th coded data reception unit.The reference numeral 1410 represents a coded data reconfiguration unit.The reference numeral 1500 represents a first audio code conversion andtransmission unit. The reference numeral 1501 represents a decodingunit. The reference numeral 1502 represents a first transmittedframe/packet coding unit. The reference numeral 1503 represents a firsterror detection code added frame/packet identification number additionunit. The reference numeral 1504 represents a second transmittedframe/packet coding unit. The reference numeral 1505 represents a firsterror detection code added frame/packet identification number additionunit. The reference numeral 1510 represents a second audio codeconversion and transmission unit.

BEST MODE FOR CARRYING OUT THE INVENTION

A description will be given of embodiments of the present invention. Inthe first embodiment of the present invention, a code conversion andtransmission apparatus includes for an integer N of 2 or larger and aninteger M of 1 or larger: a) first audio code conversion andtransmission means (102 shown in FIG. 1) for inputting compressed codeddata, and transmitting all frames or a part of frames adaptivelyselected depending on the characteristics of input audio data oraccording to a predetermined rule using predetermined transmissionmeans; b) (N−1) units of the second to N-th audio code conversion andtransmission means (104, 105, and 106 shown in FIG. 1) for decodinginput coded data, compressing and coding data at a compression rateequal to or higher than the rate of the first audio code conversion andtransmission means, and transmitting all frames of obtained coded dataor a part of frames adaptively selected depending on the characteristicof input audio data or according to a predetermined rule atpredetermined or adaptively variable time intervals using transmissionmeans the same as or different from the transmission means of the firstaudio code conversion and transmission means; and c) means for selectinga compression rate for coding of at least one of the first to N-th audiocode conversion and transmission means depending on the band availablefor each of the first to M-th transmission lines, and transmitting it tothe first to M-th transmission lines.

The code conversion and reception apparatus includes d) means (107 shownin FIG. 1) for selecting at least one transmission line from Mtransmission lines, and means (112 shown in FIG. 1) for receiving Npieces of coded data from the selected transmission line, extractingcoded data received without a transmission error or a loss, selectingaudio coded data with the lowest compression rate from the coded data inthe same frame, and outputting the selected data. The process andfunction of each means of the code conversion and transmission apparatusand the code conversion and reception apparatus can be realized by aprogram executed by a computer configuring the code conversion andtransmission apparatus and the code conversion and reception apparatus.

Embodiment

For detailed explanation about the mode for carrying out the presentinvention, the first embodiment of the present invention will beexplained referring to the drawings.

(1.A) Summary

FIG. 1 shows the configuration of the first embodiment of the presentinvention. As shown in FIG. 1, the first embodiment of the presentinvention comprises an audio data code conversion and transmissionapparatus 100, an audio data code conversion and reception apparatus 120and transmission lines 130 for transmitting coded data. The integer Nindicates the number of pieces of coded data transmitted by the codeconversion and transmission apparatus, and is 2 or larger. The integer Mindicates the number of the transmission lines 130 for transmitting Npieces of coded data, and is 1 or larger.

The code conversion and transmission apparatus 100 inputs audio datacoded by an audio coding apparatus (not shown in the drawings), codesthe input audio data into N pieces of coded data, and transmits theresultant data as first to N-th audio coded data to the first to M-thtransmission lines. As shown in FIG. 1, the unit 110 comprises first toN-th audio code conversion and transmission units 102 to 106 to transmitdata to the first to M-th transmission lines.

As shown in FIG. 1, the code conversion and transmission apparatus 100comprises M units of code converting and transmitting units 1 to M forthe first to M-th transmission lines 130. The code converting andtransmitting units 1 to M transmit coded data to M pieces of the firstto M-th transmission lines 130.

The code converting and transmitting units 1 to M comprise the first toN-th audio code conversion and transmission units 102 and 104 to 106,and output first to N-th audio streams. The code converting andtransmitting units 2 to M commonly input the audio coded data oncereceived by the code converting and transmitting unit 1. Otherwise, theyare similar in configuration to the code converting and transmittingunit 1. FIG. 1 shows only the configuration of the code converting andtransmitting unit 1 for simplicity. In the following, a description willbe made of the code converting and transmitting unit 1, but theexplanation of the code converting and transmitting units 2 to M will beomitted.

The audio data reception unit 101 of the code converting andtransmitting unit 1 receives audio coded data. The audio coded datareceived by the audio data reception unit 101 of the code converting andtransmitting unit 1 is also provided for the code converting andtransmitting units 2 to M.

The first audio code conversion and transmission unit 102 transmits allor a part of the frames of the input audio data to the code conversionand reception apparatus 120.

The input audio data is decoded by the audio data decoding unit 103, andthe second audio code conversion and transmission unit 104 compressesand codes the obtained audio data in a predetermined method at acompression rate equal to or higher than the rate of the first audiostream, and transmits the coded data to the code conversion andreception apparatus 120.

When N is 3 or larger, the third to N-th audio code conversion andtransmission units 105 to 106 code all or a part of frames coded by thefirst audio code conversion and transmission unit 102 at a compressionrate equal to or higher than the rate of the second audio codeconversion and transmission unit 104, and transmit the obtained codeddata to the code conversion and reception apparatus 120. The first toN-th audio streams are transmitted to the first to M-th transmissionlines 130.

The first to N-th audio data streams of the code converting andtransmitting units 1 to M are transmitted to the first to M-thtransmission lines 130. Depending on the available bands of the audiodata in each transmission line 130, the compression rate of the secondto N-th audio code conversion and transmission units 104 to 106 can beselected. Thus, the output of the first audio code conversion andtransmission unit 102 and the output of the second to N-th audio codeconversion and transmission units 104 to 106, whose compression rateshave been controlled, are output to the first to M-th transmission lines130. In this embodiment, data can be transmitted based on the status ofthe transmission line or the intention of the transmitter of audio data.

Instead of providing a plurality of code converting and transmittingunits 1 to M, the output of the first to N-th audio code conversion andtransmission units of one code converting and transmitting unit 1 can bedistributed to the first to M-th transmission lines 130. Furthermore,the output paths of the code converting and transmitting units 1 to Mcan be switched, and the connection of the first to M-th transmissionlines 130 can be switched.

In the code conversion and reception apparatus 120, a reception lineselection unit 107 selects at least one transmission line from Mtransmission lines 130 through which data are transmitted by the codeconversion and transmission apparatus 100, N pieces of coded data arereceived from the selected transmission lines, and decoded.

The code conversion and reception apparatus 120 comprises first to N-thcoded data reception units 108 to 111 which receive coded datatransmitted from the first to N-th audio code conversion andtransmission units 102 to 106 of the code conversion and transmissionapparatus 100 and a coded data reconfiguration unit 112 as shown in FIG.1.

The coded data reconfiguration unit 112 selects data having, forexample, the lowest compression rate from the maximum of N pieces ofcoded data received without a transmission error or a loss by the codeddata reception units 108 to 111, and outputs the selected data.

Thus, according to the present embodiment, the code conversion andtransmission apparatus which transmits audio data coded by the audiocoding apparatus, not shown in the drawings, comprises a data receptionunit 101 for receiving data from the audio coding apparatus, convertsaudio data to N pieces of coded data, and transmits each piece of datato the M transmission lines at predetermined or adaptively variable timeintervals. The second to N-th audio code conversion and transmissionmeans (first to N-th audio code conversion and transmission unit) 104 to106 code the frame coded by the first audio code conversion andtransmission unit 102 at a compression rate equal to or higher than therate of the first compressing and coding method. On the receiver side,the reception line selection unit 107 selects a transmission line, andthe coded data reconfiguration unit 112 selects coded data having thelowest compression rate and having high audio quality from the correctlyreceived coded data in a frame or packet unit, and decodes the selecteddata. The detailed explanation will be given below.

(1.B) Code Conversion and Transmission Apparatus

FIG. 2 shows the detailed configuration of the audio code conversion andtransmission apparatus according to the first embodiment of the presentinvention. For simplicity, the number N of pieces of coded data outputby the apparatus is set to 3, and the number M of transmission lines fortransmitting coded data is set to 2. In FIG. 2, a first audio codeconversion transmission unit 200 corresponds to the first audio codeconversion and transmission unit 102 shown in FIG. 1, a second audiocode conversion transmission unit 220 corresponds to the second audiocode conversion and transmission unit 104 shown in FIG. 1, a decodingunit 203 corresponds to the first audio data decoding unit 103 shown inFIG. 1, and a third audio code conversion transmission unit 230corresponds to the third audio code conversion and transmission unit 105shown in FIG. 1.

In the first audio code conversion transmission unit 200, a firsttransmission frame/packet selection unit 201 selects an adaptivelytransmitted frame from among input audio frames depending on thecharacteristic of the input audio data and the status of thetransmission line. In adaptively selecting a frame, storage means storesin advance a rule for determination whether or not a frame is selectedbased on the characteristic of audio data (for example, the parameter ofan audio signal having an influence on audio quality, sound/soundless,etc.) and the status of a transmission line (for example, the status ofan occurrence of a transmission error, etc.). The first transmissionframe/packet selection unit 201 can refer to the rule, and dynamicallyselect a frame at any time based on the comparison result with theanalysis result (or transmission status) of audio data. When thetransmission frame/packet selection unit according to another embodimentdescribed below adaptively (dynamically) selects a frame/packetaccording to the rule, a frame/packet can be selected by referring tothe rule. The rule according to which a frame/packet is selected canalso be dynamically variable.

A first error detection code added frame/packet identification numberaddition unit 202 adds an error detection code and a frame/packetidentification number for detecting a transmission error and a packetloss in output coded packet data in the reception apparatus, and thefirst audio coded data is output.

In FIG. 2, in the second audio code conversion transmission unit 220,the decoding unit 203 decodes input audio coded data.

The second compression and coding unit 206 compresses and codes thedecoded data obtained by the decoding unit 203 in a predeterminedmethod.

A second coded packet generation unit 207 codes the compressed dataobtained by the second compression and coding unit 206 into variable bitstring, and outputs the resultant data in a predetermined packet unit.

A second error detection code added frame/packet identification numberaddition unit 208 adds an error detection code and a frame/packetidentification number for detecting a transmission error and a packetloss of the coded packet data output by the second coded packetgeneration unit 207 in the reception apparatus, and outputs the secondaudio coded data.

In the third audio code conversion transmission unit 230, a thirdcompression coding unit 212 codes the audio data obtained by thedecoding unit 203 at a compression rate equal to or higher than the rateof the second compression and coding unit 206.

A third coded packet generation unit 213 codes the compressed dataobtained by the third compression coding unit 212 into variable bitstring, and outputs the coded data in a predetermined packet unit.

A third error detection code added frame/packet identification numberaddition unit 214 adds an error detection code and a frame/packetidentification number for detection by the reception apparatus of atransmission error and a packet loss in the compressed packet dataoutput by the third coded packet generation unit 213, outputs the thirdaudio coded data, and predetermined transmission means transmits thedata in a packet unit.

In the present embodiment, M is set to 2, and N is set to 3. Therefore,the first to third audio code conversion and transmission data aretransmitted to each of the two transmission lines.

In the present embodiment, the output of the second to N-th coded datacan be separately transmitted from the output of the first coded data attime intervals, or the second to N-th coded data can be multiplexed withthe first coded data and transmitted.

The first error detection code added frame/packet identification numberaddition unit 202 is provided to add an error detection code and aframe/packet identification number to the first coded data output fromthe first transmission frame/packet selection unit 201. However, it canbe omitted if the information has already been added to the input audiopacket data. If the transmission error and the packet loss of thetransmitted coded packet data can be detected by the code conversion andreception apparatus in any other methods, they can be used. For example,if there is a mechanism of detecting a transmission error in atransmission line of the first coded packet, then it is not necessary toadd an error detection code by the first error detection code addedframe/packet identification number addition unit 202. In anotherexample, if information for identification of a frame and a packet iscontained in the coded data output from the first transmissionframe/packet selection unit 201, it is not necessary to add aframe/packet identification number by the first error detection codeadded frame/packet identification number addition unit 202.

Similarly, the second error detection code added frame/packetidentification number addition unit 208 is provided to add an errordetection code and a frame/packet identification number to the secondcoded data. However, any method capable of detecting a transmissionerror and a packet loss of transmitted coded data by a code conversionand reception apparatus can be used.

Similarly, the third error detection code added frame/packetidentification number addition unit 214 is provided to add an errordetection code and a frame/packet identification number to the thirdcoded data, but any method capable of detecting a transmission error anda packet loss of transmitted coded data by a code conversion andreception apparatus can be used.

In a further preferable practical example of the above-mentionedembodiment, the audio code conversion and transmission apparatus isconnected to an Internet communications network, compresses an audiosignal input using a microphone, etc. into coded data according to, forexample, an MPEG-4 advanced audio coding (AAC) system, and inputs datatransmitted using a real time transport protocol (RTP)/user datagramprotocol (UDP)/Internet protocol (IP) protocol.

In FIG. 2, the second compression and coding unit 206 and the thirdcompression coding unit 212 performs a compressing process using amodified discrete cosine transform (MDCT) and quantization. The thirdcompression coding unit 212 compresses data such that the compressionrate of the third coded data can be equal to or higher than thecompression rate of the first coded data in the method of quantizing anMDCT coefficient using a quantization parameter larger than that of thesecond compression and coding unit 206 and in the method of adaptivelycutting a higher order MDCT.

The decoding unit 203 performs inverse quantization and an inverse MDCTtransform.

The second coded packet generation unit 207 codes a quantized MDCTcoefficient, etc. output from the second compression and coding unit 206according to the syntax prescribed by the MPEG-4AAC.

Similarly, the third coded packet generation unit 213 codes a quantizedMDCT coefficient, etc. output from the third compression coding unit 212according to the syntax prescribed by the MPEG-4 AAC.

The first error detection code added frame/packet identification numberaddition unit 202, the second error detection code added frame/packetidentification number addition unit 208, and the third error detectioncode added frame/packet identification number addition unit 214 generateUDP datagram including a check-sum for detection of an error, andtransmit it to a code conversion and reception apparatus connected tothe Internet.

(1.C) Code Conversion and Reception Apparatus

FIG. 3 shows the detailed configuration of the code conversion andreception apparatus 120 according to the first embodiment of the presentinvention shown in FIG. 1. In FIG. 3, the code conversion and receptionapparatus comprises a reception line selection unit 300, first to thirdcoded data reception units 320 to 340, and a coded data reconfigurationunit 310.

The reception line selection unit 300 selects a transmission line forthe code conversion and reception apparatus receiving audio data.

In the first coded data reception unit 320, a first packet receptionbuffer 301 receives the first coded packet data transmitted from thecode conversion and transmission apparatus. A first coded dataextraction unit 302 extracts audio coded data from the packet datareceived by the first packet reception buffer 301. A first error/packetloss detection unit 303 detects a bit error and/or a packet lossgenerated when the first coded packet data is transmitted.

In the second coded data reception unit 330, a second packet receptionbuffer 304 receives the second coded packet data transmitted from thecode conversion and transmission apparatus. A second coded dataextraction unit 305 extracts audio coded data from the packet datareceived by the second packet reception buffer 304. A seconderror/packet loss detection unit 306 detects a bit error and/or a packetloss generated when the second coded packet data is transmitted.

In the third coded data reception unit 340, a third packet receptionbuffer 307 receives the third coded packet data transmitted from thecode conversion and transmission apparatus. A third coded dataextraction unit 308 extracts audio coded data from the packet datareceived by the third packet reception buffer 307. A third error/packetloss detection unit 309 detects a bit error and/or a packet lossgenerated when the third coded packet data is transmitted.

A coded data reconfiguration unit 310 reconfigures two pieces of codeddata transmitted from the code conversion and transmission apparatusinto one piece of coded data according to the result of detecting anerror and/or packet loss by the first error/packet loss detection unit303, the second error/packet loss detection unit 306, and the thirderror/packet loss detection unit 309.

The coded data reconfiguring procedure by the coded data reconfigurationunit 310 in the present embodiment will be explained below by referringto the flowchart shown in FIG. 4. In the series of procedures shown inFIG. 4, the coded data reconfiguring process of the n-th frame isperformed on a given integer n.

In step S401, control is delayed until the time obtained by adding thepredetermined maximum delay time to the time when all coded data in then-th frame should arrive at the first packet reception buffer 301 andthe second packet reception buffer 304, and then control is passed tostep S402.

In step S402, based on the detection result of an error and a packetloss by the first error/packet loss detection unit 303, it is determinedwhether or not there is any packet loss or bit error in the n-th framedata in the first packet reception buffer 301. If the first packetreception buffer 301 receives all coded data in the n-th frame, andthere is no data error detected, then control is passed to step S403.Otherwise, control is passed to step S404.

When control is passed to step S403, the coded data of the n-th frameoutput by the first coded data extraction unit 302 is output, therebyterminating the coded data reconfiguring process.

When control is passed to step S404, it is determined whether or notthere is no packet loss or bit error in the n-th frame data in thesecond packet reception buffer 304 based on the detection result of theerror and packet loss in the second error/packet loss detection unit306. When the second packet reception buffer 304 receives all coded datain the n-th frame and there is no data error detected, control is passedto step S405. Otherwise, control is passed to step S406.

When control is passed to step S406, it is determined whether or notthere is no packet loss or bit error in the n-th frame data in thesecond packet reception buffer 304 based on the detection result of theerror and/or packet loss in the third error/packet loss detection unit309. When the third packet reception buffer 307 receives all coded datain the n-th frame and there is no data error detected, control is passedto step S407. Otherwise, control is passed to step S403.

In step S407, the coded data in the n-th frame output by the third codeddata extraction unit 308 is output as the coded data to be decoded,thereby terminating the coded data reconfiguring process.

Described above is the coded data reconfiguring procedure by the codeddata reconfiguration unit 310.

In the present embodiment, any method of detecting a transmission errorand/or error packet loss in the first coded data by the firsterror/packet loss detection unit 303 can be used. For example, thedetection can be performed using an error detection code and aframe/packet number added by the code conversion and transmissionapparatus according to the present embodiment. When an error detectingfunction is provided for a transmission line of coded data, thedetection result can also be used. When the information designating acoded frame is included in the coded data, the information included inthe coded data can be used.

Similarly, any method of detecting a transmission error and/or errorpacket loss in the second coded data by the second error/packet lossdetection unit 306 can be used.

Also, any method of detecting a transmission error and/or error packetloss by the third error/packet loss detection unit 309 can be used.

In the coded data reconfiguring procedure by the coded datareconfiguration unit 310, the method of waiting reception of the n-thframe coded data in step S401 can be replaced with any method used aslong as a packet loss can be detected while suppressing the packettransmission delay within a predetermined range.

In the coded data reconfiguring procedure by the coded datareconfiguration unit 310, in step S406, when a transmission error or apacket loss is detected in the coded data received in the thirdreception packet buffer, that is, when a transmission error or a packetloss has occurred in all the first to third coded data, the coded datareconfiguration unit 310 can take any other countermeasures.

In the present embodiment, control is passed to step S403, and the firstcoded data is output as coded data to be decoded. However, for example,the output of the n-th frame can be suppressed, and the audio data inthe (n−1)th frame which is output immediately before can be output asthe n-th frame, etc.

In a preferred practical example of the embodiment of the presentinvention, the code conversion and reception apparatus is connected toan Internet communications network, receives packet data transmittedusing an RTP/UDP/IP protocol from the code conversion and transmissionapparatus connected to the Internet communications network at anotherpoint, converts the audio coded data contained in the received UDPdatagram, and outputs the result to a decoder. The audio coded data isin accordance with the MPEG-4 AAC system. The first error/packet lossdetection unit 303, the second error/packet loss detection unit 306, andthe third error/packet loss detection unit 309 can detect a transmissionerror by calculating the checksum included in the UDP datagram.

Furthermore, since the code conversion and reception apparatus only hasto decode at least one piece of data in the three pieces of receivedcoded data, the necessary arithmetic complexity does not greatlyincrease as compared with the normal audio coding apparatus.

(1.D) Transmission Mode of Coded Packet Data

According to the present invention, the first to second coded packetdata can be transmitted in any method from the code conversion andtransmission apparatus to the code conversion and reception apparatus.However, to enhance the effect of the present invention, a method inwhich the relation between a bit error and a packet loss occurring inthe first coded packet data and a bit error and a packet loss occurringin the second coded packet data obtained by coding the same frame can beminimized is preferable. FIG. 5 shows a preferable mode of transmittingcoded packet data.

In FIG. 5, the reference numeral 501 denotes an audio code conversionapparatus which has been explained by referring to FIGS. 1 and 2. Delayaddition units 502 and 503 add predetermined or adaptively variabledelay time to the second and third coded packet data output from theaudio code conversion apparatus 501. A multiplexing unit 504 multiplexesthe first coded data output from the audio code conversion apparatus 501with the second coded data output from the delay addition unit 502 andthe third coded data output from the delay addition unit 503, andtransmits the result to a transmission line. A transmission line 505transmits the data multiplexed by the delay addition unit 503 from thetransmission apparatus to the reception apparatus. Similarly, amultiplexing unit 508 and a transmission line 509 transmit the data tothe second transmission line.

In the delay addition units 502 and 503, the delay time added to thesecond and third coded data depends on the maximum burst time of a biterror and a packet loss occurring in the transmission line 505. Thedelay amount depends on the bit rate, the buffer size, etc. taken intoaccount. Thus, even when a burst error occurs in the transmission line505, the probability that the first to third coded data can be affectedby an influence of an error. Therefore, the outstanding degradation ofsound quality due to a loss of frame coded data can be reduced. Thelongest burst time due to a packet loss depends on the actualmeasurement, etc., and the delay set by the delay addition unit is setbased on the buffer size of a reception apparatus and a transfer rate(bit rate) of a transmission line.

Similarly, the delay time applied to the second to third coded data bydelay addition units 506 and 507 depends on the maximum burst time of abit error and a packet loss occurring in the transmission line 509.Thus, even if a burst error occurs in the transmission line 509, thereis a small probability that the first to third coded data obtained bycoding data in the same frame have an influence of the error. Therefore,the occurrence of outstanding degradation in audio quality due to a lossof frame coded data can be suppressed. The delay addition unit, or thedelay addition unit and the multiplexing unit can be provided in theaudio code conversion apparatus 501.

(1.E) Advantages

According to the first embodiment, the audio code conversion andtransmission apparatus converts the same audio data into N pieces (N=3in this example) of coded data, and transmits the resultant data atpredetermined or adaptively variable time intervals. The first audiocode conversion and transmission unit outputs input audio data frame byadaptively selecting depending on the characteristic of audio data oraccording to a predetermined rule. The second audio code conversion andtransmission unit decodes input audio data, and outputs the decoded databy coding the data at a compression rate equal to or higher than therate of the input data. The third audio code conversion and transmissionunit codes a frame coded by the second audio code conversion andtransmission unit.

The code conversion and reception apparatus receives data from at leastone transmission line in the M units of transmission lines, selectscoded data having a low compression rate and high audio quality frame byframe from the correctly received coded data, and outputs the selecteddata.

As a result, even when a less reliable transmission line in which highburst transmission error and packet loss frequently occur is used, theprobability that N pieces of coded data are transmitted with errors canbe reduced, and the outstanding degradation can be prevented from beinggenerated in decoded audio quality after transmission.

Furthermore, by enhancing the compression rate of the second to thirdcoded data, the increase of transmission bands during the transmissionof coded data can be suppressed.

Additionally, depending on the available band, the first to third codeddata can be transmitted to a plurality of transmission lines havingdifferent bands, and the influence of an error in the transmission linecan be reduced.

According to the present embodiment, the code conversion andtransmission apparatus and the code conversion and reception apparatusare combined, but they can be independently used. The order of thepackets of the first to N-th code converted data can be shuffled formultiplexing by an interleave method or the like.

[Second Mode for Carrying Out the Present Invention]

In the second embodiment of the present invention, the code conversionand transmission apparatus includes for an integer N of 2 or larger andan integer M of 1 or larger: a) first audio code conversion andtransmission means for inputting compressed coded packet data, andtransmitting all packets or a part of packets adaptively selecteddepending on the characteristics of input audio data or according to apredetermined rule using predetermined transmission means; b) (N−1)units of the second to N-th audio code conversion and transmission meansfor decoding input coded packet data, compressing and coding data intopacket data at a compression rate equal to or higher than the rate ofthe first audio code conversion and transmission means, and transmittingall obtained packet data or a part of packet data adaptively selecteddepending on the characteristic of input audio data or according to apredetermined rule at predetermined or adaptively variable timeintervals using transmission means the same as or different from thetransmission means of the first audio code conversion and transmissionmeans; and c) means for selecting a compression rate for coding of atleast one of the first to N-th audio code conversion and transmissionmeans, and transmitting it to the first to M-th transmission lines.

The code conversion and reception apparatus includes d) selection meansfor selecting at least one transmission line from M transmission lines,receiving up to N pieces of coded data from the selected transmissionline, selecting coded packet data having the lowest compression ratefrom the packet data received without a transmission error or a loss,and outputting the selected data. The process and function of each meansof the code conversion and transmission apparatus and the codeconversion and reception apparatus can be realized by a program executedby a computer configuring the code conversion and transmission apparatusand the code conversion and reception apparatus.

Second Embodiment

For detailed explanation about the second mode for carrying out thepresent invention, the second embodiment of the present invention willbe explained below.

(2.A) Summary

The configuration and the operation of the present embodiment issubstantially the same as those of the first embodiment. As shown inFIG. 1, the embodiment of the present invention comprises the codeconversion and transmission apparatus 100, the code conversion andreception apparatus 120, and the transmission lines 130 for transmittingcoded data. The integer N indicates the number of coded data transmittedby the code conversion and transmission apparatus, and is 2 or larger.The integer M indicates the number of transmission lines fortransmitting N pieces of coded data, and is 1 or larger.

The configuration of the code conversion and transmission apparatus 100is substantially the same as that according to the first invention, butthe operation of each unit forming the apparatus is somewhat different.Described below are the differences.

The audio coded data in the input frame coded by the first audio codeconversion and transmission unit (first audio coded frame 1 transmissionunit) 102 is configured by one or more pieces of packet data, and eachpiece of packet coded data is coded compressed data. The first audiostream transmits all or a part of packets of input audio data to thecode conversion and reception apparatus 120.

The second audio code conversion and transmission unit (second audiocoded frame 1 transmission unit) 104 decodes input audio data,compresses and codes the obtained audio data at a compression rate equalto or higher than the rate of the first audio stream, and transmits thecoded data to the code conversion and reception apparatus 120.

The third to N-th audio code conversion and transmission units 105 and106 code all or a part of packets coded by the second audio codeconversion and transmission unit at a compression rate equal to orhigher than the rate of the second audio code conversion andtransmission unit, and transmits the obtained coded packet data to thecode conversion and reception apparatus 120. The operations other thanthe above-mentioned operation are basically the same as those in thefirst embodiment. In the second embodiment, depending on the bandavailable in the transmission of audio data in each transmission line130, the compression rate of the second to N-th audio code conversionand transmission units 104 to 106 can be selected. The output of thefirst to N-th audio code conversion and transmission units 102, 104 to106 is output to the first to M-th transmission lines 130. In thepresent embodiment, data can be transmitted based on the status of thetransmission line or the intention of the transmitter of audio data.

The configuration of the code conversion and reception apparatus 120 issubstantially the same as the first embodiment, but the operation ofeach unit configuring the apparatus is somewhat different. Describedbelow are the differences.

The coded data reconfiguration unit 112 selects a packet having thelowest compression rate from among up to N pieces of coded packet dataincluding the compressed data in the same area of the same framereceived without a transmission error or a loss by the first to N-thcoded data reception unit as in the first embodiment. The data isselected in a packet unit transmitted by the code conversion andtransmission apparatus. The operations other than the above-mentionedoperation are basically the same as those in the first embodiment.

(2.B) Code Conversion and Transmission Apparatus

The operation and the configuration of the code conversion andtransmission apparatus according to the present invention aresubstantially the same as those of the code conversion and transmissionapparatus according to the first embodiment shown in FIG. 2. Only theoperations of the first coded packet selection unit 201, the secondcoded packet generation unit 207, the third coded packet generation unit213, the first error detection code added frame/packet identificationnumber addition unit 202, the second error detection code addedframe/packet identification number addition unit 208, and the thirderror detection code added frame/packet identification number additionunit 214 are different. Described below are the differences.

The first error detection code added frame/packet identification numberaddition unit 202, the second error detection code added frame/packetidentification number addition unit 208, and the third error detectioncode added frame/packet identification number addition unit 214 operatesuch that the same packet identification number can be assigned to thecoded packet data in the same frame. The operations of the processingunits other than the above-mentioned operation are the same as those inthe first embodiment.

(2.C) Code Conversion and Reception Apparatus

The configuration and the operations of the audio code conversion andreception apparatus according to the present embodiment aresubstantially the same as those of the audio code conversion andreception apparatus according to the first embodiment, and only theoperations of the coded data reconfiguration unit 310 shown in FIG. 3are different. Described below are the differences.

The coded data reconfiguring procedure by the coded data reconfigurationunit 310 in the present embodiment will be explained below by referringto the flowchart shown in FIG. 6. In the series of procedures shown inFIG. 6, the coded data reconfiguring process of the n-th frame isperformed on a given integer n.

In step S601, control is delayed until the time obtained by adding thepredetermined maximum delay time to the time when all coded data in then-th frame should arrive at the first packet reception buffer 301, thesecond packet reception buffer 304, and the third packet receptionbuffer 307, and then control is passed to step S602.

In step S 602, a variable for storage of a packet number stores theminimum value of the packet number of the n-th frame, and a variable bstores the maximum value of the packet number of the n-th frame.

In step S603, the value of the variable is substituted for the variablei for storage of a packet number, and the repeating process is startedfrom step S604.

In step S604, it is determined according to the detection result of anerror and a packet loss in the first error/packet loss detection unit303 whether or not an i-th packet exists and there are bit errors in thefirst packet reception buffer 301. When the i-th packet in the n-thframe is received in the first packet reception buffer 301, and thereare no errors in the data, control is passed to step S605. Otherwise,control is passed to step S606.

When control is passed to step S605, the coded data in the n-th frameoutput by the first coded data extraction unit 302 is output as thecoded data to be decoded, and control is passed to step S610.

When control is passed to step S606, it is determined according to adetection result of an error and a packet loss by the seconderror/packet loss detection unit 306 whether or not there is the i-thpacket and there are bit errors in the second packet reception buffer304. When the second packet reception buffer 304 receives the i-thpacket in the n-th frame, and there are no data errors detected, controlis passed to step S607. Otherwise, control is passed to step S608.

In step S607, the coded data in the n-th frame output by the secondcoded data extraction unit 305 is output as coded data to be decoded,and control is passed to step S610.

When control is passed to step S608, it is determined according to adetection result of an error and a packet loss by the third error/packetloss detection unit 309 whether or not there is the i-th packet andthere are bit errors in the third packet reception buffer 307. When thethird packet reception buffer 307 receives the i-th packet in the n-thframe, and there are no data errors detected, control is passed to stepS609. Otherwise, control is passed to step S610.

In step S610, the variable i is incremented by 1. In step S611, it isdetermined whether or not the variable i exceeds the value of thevariable b. If it does not exceed, the processes from step S604 arerepeated.

In step S610, when the variable i exceeds the variable b, a series ofrepeated processes are performed, thereby terminating the n-th framecoded data reconfiguring process.

The operations of the coded data reconfiguration unit 310 according tothe present embodiment have been described above. The method of waitingfor the reception of the n-th frame coded data at step S601 in the codeddata reconfiguring procedure by the coded data reconfiguration unit 310according to the present embodiment can be replaced by any method ofdetecting a packet loss with the transmission delay being maintained ina predetermined range.

(2.D) Advantages

According to the second embodiment, the audio code conversion andtransmission apparatus codes the same audio data into N pieces (N=3 inthis example) of coded data, and transmits the resultant data atpredetermined or adaptively variable time intervals.

The second to third audio code conversion and transmission means codesan area including a packet converted by the first audio code conversionand transmission means.

The code conversion and reception apparatus selects the coded datahaving a low compression rate and high audio quality from the correctlyreceived coded data in a packet unit and then decodes the data.

As a result, even when a less reliable transmission line in which highburst transmission error and packet loss frequently occur is used, theprobability that 3 pieces of coded data are transmitted with errors canbe reduced, and the outstanding degradation can be prevented from beinggenerated in decoded audio quality after transmission.

Furthermore, by enhancing the compression rate of the second to thirdcoded data, the increase of transmission bands during the transmissionof coded data can be suppressed.

Additionally, depending on the available band, the first to third codeddata can be transmitted to a plurality of transmission line havingdifferent bands, and the influence of an error in the transmission linecan be reduced. Since the code conversion and reception apparatus onlyhas to decode one of the three received coded data, the arithmeticcomplexity is not greatly increased as compared with the common audiodecoding apparatus.

According to the present embodiment, the code conversion andtransmission apparatus and the code conversion and reception apparatusare combined, but they can be independently used.

[Third Mode for Carrying Out the Present Invention]

In the third embodiment of the present invention, the code conversionand transmission apparatus includes, for an integer N of 2 or larger andan integer M of 1 or larger: a) first audio code conversion andtransmission means for inputting compressed coded data, compressing andcoding all frames of decoded audio data or a part of frames selecteddepending on the characteristic of input audio data or according to apredetermined rule at a compression rate equal to or higher than therate of the input audio data, and transmitting obtained coded data usingpredetermined transmission means; b) (N−1) units of the second to N-thaudio code conversion and transmission means for coding all frames codedby the first audio code conversion and transmission means or a part offrames adaptively selected depending on the characteristic of inputaudio data or according to a predetermined rule at a compression rateequal to or higher than the rate of the first audio code conversion andtransmission means, and transmitting obtained coded data atpredetermined or adaptively variable time intervals using transmissionmeans the same as or different from the transmission means of the firstaudio code conversion and transmission means; and c) means for selectinga compression rate for coding for the first to N-th audio codeconversion and transmission means depending on the band available foreach of the first to M-th transmission lines, and transmitting it to thefirst to M-th transmission lines.

The code conversion and reception apparatus includes d) means forselecting at least one transmission line from M transmission lines,receiving N pieces of coded data from the selected transmission line,extracting coded data received without a transmission error or a loss,selecting audio coded data having the lowest compression rate from thecoded data in the same frame, and outputting the selected data. Theprocess and function of each means of the code conversion andtransmission apparatus and the code conversion and reception apparatuscan be realized by a program executed by a computer configuring the codeconversion and transmission apparatus and the code conversion andreception apparatus.

Third Embodiment

For detailed explanation about the third mode for carrying out thepresent invention, the third embodiment of the present invention will beexplained referring to the drawings.

(3.A) Summary

FIG. 7 shows the configuration of the third embodiment of the presentinvention. As shown in FIG. 7, the embodiment of the present inventioncomprises a code conversion and transmission apparatus for audio data(also referred to as an “audio code conversion and transmissionapparatus”) 700, a code conversion and reception apparatus (alsoreferred to as an “audio code conversion and reception apparatus”) 720,and transmission lines 730 for transmitting coded data. The integer Nindicates the number of coded data transmitted by the code conversionand transmission apparatus 700, and is assumed to be 2 or larger. Theinteger M indicates the number of transmission lines by which N piecesof coded data are transmitted, and is assumed to be 1 or larger.

The audio code conversion and transmission apparatus 700 decodes inputaudio coded data, compresses and codes the obtained audio data at acompression rate equal to or higher than the rate of the input data, andtransmits code converted data to the audio code conversion and receptionapparatus 720. The input audio data is coded into N pieces of codeddata, and transmitted as the first to N-th audio coded data to the firstto M-th transmission lines. As shown in FIG. 7, the apparatus comprisescode converting units 1 to N, and each code converting unit comprises Nunits of first to N-th audio code conversion and transmission units(first to N-th audio code conversion and transmission units) 703, 704,and 705.

An audio data reception unit 701 receives audio data.

An audio data decoding unit 702 decodes input audio coded data.

The first audio code conversion and transmission unit 703 compresses andcodes in a predetermined method on a frame input to the code conversionand transmission apparatus, and the obtained coded data is transmittedto the audio code conversion and reception apparatus 720.

The second to N-th audio code conversion and transmission units 704 and705 code all or a part of frames coded by the first audio codeconversion and transmission unit 703 at a compression rate equal to orhigher than the rate of the first audio code conversion and transmissionunit 703, and transmit the obtained coded data to the audio codeconversion and reception apparatus 720. The first to N-th audio streamsare transmitted to the first to M-th transmission lines 730. Eachtransmission line 730 can control by selecting the compression rate forcoding of the first to N-th audio code conversion and transmission units703 to 705 depending on the available bands for transmission of audiodata. The output of the first to N-th audio code conversion andtransmission units 703 to 705, whose compression rate in coding iscontrolled, is output to the first to M-th transmission lines 730, anddata can be transmitted based on the status of the transmission line orthe intention of the transmitter of audio data.

In the audio code conversion and reception apparatus 720, a receptiontransmission line selection unit 706 selects at least one transmissionline from the M transmission lines transmitted by the audio codeconversion and transmission apparatus, receives N pieces of coded datafrom the selected transmission lines, and then decodes the data.

As shown in FIG. 7, the audio code conversion and reception apparatus720 comprises first to N-th coded data reception units 707 to 709 forreceiving the coded data transmitted from the first to N-th audio codedframe 1 transmission units 703 to 705 provided in the code conversionand transmission apparatus 700, and the coded data reconfiguration unit710.

The coded data reconfiguration unit 710 selects the data having thelowest compression rate from among up to N pieces of coded data receivedwithout a transmission error or a loss by the coded data reception unit707 to 709, and outputs the selected data.

(3.B) Code Conversion and Transmission Apparatus:

FIG. 8 shows the detailed configuration of the audio code conversion andtransmission apparatus according to the third embodiment of the presentinvention. For simplicity, the number N of the coded data to be outputby the apparatus is assumed to be 2, and the number M of thetransmission lines for transmitting the coded data is assumed to be 2.The apparatus corresponds to the configuration including the first audiocode conversion and transmission unit 703 and the second audio codeconversion and transmission unit 704 shown in FIG. 7.

In FIG. 8, a first audio coded conversion and transmission unit 800comprises: a decoding unit 801 for decoding input audio data; a firstcompression and coding unit 804 for compressing and coding the data; afirst coded packet generation unit 805 for coding the compressed dataobtained by the first compression and coding unit 804 into a variablelength bit string, and outputting the result in a predetermined packetunit; and a first error detection code frame/packet identificationnumber addition unit 806 for adding an error detection code and aframe/packet identification number for detecting a transmission errorand a packet loss of the coded packet data output by the first codedpacket generation unit 805 by the reception apparatus. The first audiocoded data packet is transmitted by predetermined transmission means ina packet unit.

In FIG. 8, a second audio coded conversion and transmission unit 820(corresponding to the second audio code conversion and transmission unit704) comprises a second compression and coding unit 810 for coding dataat a compression rate equal to or higher than the rate of the firstcompression and coding unit 804; a second coded packet generation unit811 for coding compressed data obtained by the second compression andcoding unit 810 into a variable length bit string, and outputting theresult in a predetermined packet unit; and a second error detection codeadded frame/packet identification number addition unit 812 for adding anerror detection code and a frame/packet identification number fordetecting by the receiving apparatus a transmission error and a packetloss of the compressed packet data output by the second coded packetgeneration unit 811. The second audio coded data packet is transmittedby a predetermined transmission means in a packet unit.

In the present embodiment, M and N are assumed to be 2. Therefore, thefirst and second audio code conversion and transmission data packets aretransmitted to the two transmission lines.

In the present embodiment, the first error detection code addedframe/packet identification number addition unit 806 adds an errordetection code and a frame/packet identification number to the firstcoded packet data output from the first coded packet generation unit805. However, any method can be applied so far as a transmission errorand a packet loss of the transmitted coded packet data can be detectedby the code conversion and reception apparatus. For example, when thereis a mechanism of detecting a transmission error in the transmissionline of the first coded packet, it is not necessary for the first errordetection code frame/packet identification number addition unit 806 toadd an error detection code. For another example, if there isinformation for identification of a frame and a packet in the coded dataoutput from the first coded packet generation unit 805, it is notnecessary to add a frame/packet identification number by the first errordetection code frame/packet identification number addition unit 806.

Similarly, the second error detection code added frame/packetidentification number addition unit 812 adds an error detection code anda frame/packet identification number to the second coded packet data.However, any other methods can be applied so far as a transmission errorand a packet loss of the transmitted coded packet data can be detectedby the code conversion and reception apparatus.

An example of more preferably embodying the above-mentioned presentembodiment is the same as that according to the first embodiment of thepresent invention.

(3.C) Code Conversion and Reception Apparatus

The audio code conversion and reception apparatus (720 shown in FIG. 7)according to the third embodiment of the present invention has the sameconfiguration as shown in FIG. 3. In FIG. 3, the number M of thetransmission lines is 3, but M=2 in the present embodiment. Therefore,there is no third coded data reception unit 340 (refer to FIG. 3) of thecode conversion and reception apparatus in the present embodiment.Furthermore, since M is 2, the procedure of the operation of the codeddata reconfiguration unit 310 is different from that shown in FIG. 3.

The operation procedure by the coded data reconfiguration unit 310 inthe present embodiment will be explained below by referring to theflowchart shown in FIG. 9. In the series of procedures shown in FIG. 9,the coded data reconfiguring process of the n-th frame is performed on agiven integer n.

In step S901, control is delayed until the time obtained by adding thepredetermined maximum delay time to the time when all coded data in then-th frame should arrive at the first packet reception buffer 301 andthe second packet reception buffer 304 (refer to FIG. 3), and thencontrol is passed to step S902.

In step S902, based on the detection result of an error and a packetloss by the first error/packet loss detection unit 303, it is determinedwhether or not there is any packet loss or bit error in the n-th framedata in the first packet reception buffer 301. If the first packetreception buffer 301 receives all coded data in the n-th frame, andthere is no data error detected, then control is passed to step S903.Otherwise, control is passed to step S904.

When control is passed to step S903, the coded data of the n-th frameoutput by the first coded data extraction unit 302 is passed to thevariable length decoding unit (not shown in FIG. 3; for example,corresponding to the decoding apparatus shown in FIG. 15) as coded datato be decoded, thereby terminating the coded data reconfiguring process.

When control is passed to step S904, it is determined whether or notthere is no packet loss or bit error in the n-th frame data in thesecond packet reception buffer 304 based on the detection result of theerror and packet loss in the second error/packet loss detection unit306. When the second packet reception buffer 304 receives all coded datain the n-th frame and there is no data error detected, control is passedto step S905. Otherwise, control is passed to step S903.

In step S905, the coded data of n-th frame output by the second codeddata extraction unit 305 is passed to the variable length decoding unit(not shown in FIG. 3; for example, corresponding to the decodingapparatus shown in FIG. 15) as the coded data to be decoded, therebyterminating the coded data reconfiguring process.

The operations of other units according to the present embodiment and apreferable example are the same as those according to the firstembodiment.

(3.D) Advantages

According to the above-mentioned third embodiment, the audio codeconversion and transmission apparatus decodes the input audio data,codes the same audio data into two pieces of coded data, and transmitsthem at predetermined or adaptively variable time intervals.

The second audio code conversion and transmission means codes a codedframe coded by the first audio coded transmission means.

The code conversion and reception apparatus selects coded data having alow compression rate and high audio quality from the correctly receivedcoded data in a frame unit, and outputs the selected data. As a result,even when a less reliable transmission line in which high bursttransmission error and packet loss frequently occur is used, theprobability that two pieces of coded data are transmitted with errorscan be reduced, and the outstanding degradation can be prevented frombeing generated in decoded audio quality after transmission.

Furthermore, by enhancing the compression rate of the second coded data,the increase of transmission bands during the transmission of secondcoded data can be suppressed. Additionally, depending on the status of atransmission line and the intention of an audio transmitter or an audioreceiver, the first to second coded data can be transmitted to aplurality of transmission lines having different bands, and theinfluence of an error in the transmission line can be reduced.

Additionally, the code conversion and reception apparatus can decode atleast one piece of data from the two pieces of received coded data,thereby suppressing the increase of necessary arithmetic complexity ascompared with the common audio decoding apparatus.

According to the present embodiment, the code conversion andtransmission apparatus and the code conversion and reception apparatusare combined, but they can be independently used. The first to N-th codeconverted data can be arranged using interleaving.

[Fourth Mode for Carrying Out the Present Invention]

In the fourth embodiment of the present invention, the code conversionand transmission apparatus includes for an integer N of 2 or larger andan integer M of 1 or larger: a) first audio code conversion andtransmission means for decoding input coded packet data, compressing andcoding the data at a compression rate equal to or higher than the rateof the input audio data, and transmitting the obtained one or morepieces of coded packet data using predetermined transmission means; b)(N−1) units of the second to N-th audio code conversion and transmissionmeans for coding all packet data coded by the first audio codeconversion and transmission means or a part of packet data adaptivelyselected depending on the characteristic of input audio data oraccording to a predetermined rule into packet data including the samearea as the packet data at a compression rate equal to or higher thanthe rate of the first audio code conversion and transmission means, andtransmitting the obtained coded packet data at predetermined oradaptively variable time intervals using transmission means the same asor different from the transmission means of the first audio codeconversion and transmission means; and c) means for selecting acompression rate of the first to N-th audio code conversion andtransmission means depending on the band available for the first to M-thtransmission line, and transmitting it to the first to M-th transmissionlines.

The code conversion and reception apparatus includes d) selection meansfor selecting at least one transmission line from M transmission lines,receiving N pieces of coded data from the selected transmission line,selecting coded packet data which has the lowest compression rate fromthe packet data of the same frame received without a transmission erroror a loss, and outputting the selected data. The process and function ofeach means of the above-mentioned code conversion and transmissionapparatus and code conversion and reception apparatus can be realized bythe program executed by the computer configuring the above-mentionedcode conversion and transmission apparatus and code conversion andreception apparatus.

Fourth Embodiment

For detailed explanation about the fourth mode for carrying out thepresent invention, the fourth embodiment of the present invention willbe explained referring to the drawings.

(4.A) Summary

The configuration and the operation of the present embodiment aresubstantially the same as those according to the third embodiment, andcomprises the audio code conversion and transmission apparatus 700, thecode conversion and reception apparatus 720, and the transmission lines730 for transmitting coded data as shown in FIG. 7. The integer Nindicates the number of pieces of coded data transmitted by the codeconversion and transmission apparatus, and is 2 or larger. The integer Mindicates the number of the transmission lines for transmitting N piecesof coded data, and is 1 or larger.

The configuration of the audio code conversion and transmissionapparatus is substantially the same as that according to the thirdembodiment, but the operation of each unit forming the apparatus issomewhat different. The apparatus decodes input audio coded data,compresses and codes the obtained audio data at a compression rate equalto or higher than the rate of the input audio data, and transmits codeconverted data to the audio code conversion and reception apparatus. Thecoded data of the input frame coded by the first audio code conversionand transmission unit 703 is configured by one or more pieces of packetdata. The second to N-th audio code conversion and transmission unit 704to 705 code all or a part of packets coded by the first audio codeconversion and transmission unit 703 at a compression rate equal to orhigher than the rate of the first audio code conversion and transmissionunit 703, and transmits the obtained coded packet data to the audio codeconversion and reception apparatus. The operations other than thosedescribed above are basically the same as those according to the thirdembodiment.

The configuration of the audio code conversion and reception apparatusis substantially the same as that according to the third embodiment, butthe operation of each unit forming the apparatus is somewhat different.The differences will be described below. The coded data reconfigurationunit 710 selects a packet having the lowest compression rate as thecoded data to be decoded from among up to N pieces of coded packet dataincluding the compressed data in the same area of the same frame andreceived without a transmission error or a packet loss by the first toN-th coded data reception units 707, 708, and 709 as in the thirdembodiment. The selection is performed on each packet data transmittedby the code conversion and transmission apparatus. The operations otherthan the above-mentioned operations are basically the same as those inthe third embodiment. In the embodiment, depending on the band availablein the transmission of audio data in each transmission line 730, thecompression rate for coding by the first to N-th audio code conversionand transmission units 703 to 705 is selected. The output of the firstto N-th audio code conversion and transmission units 703 to 705 isoutput to the first to M-th transmission lines 730, and data can betransmitted based on the status of the transmission line or theintention of the transmitter of audio data.

(4.B) Code Conversion and Transmission Apparatus

The configuration and operation of the audio data code conversion andtransmission apparatus according to the present embodiment aresubstantially the same as those of the audio data code conversion andtransmission apparatus according to the third embodiment shown in FIG.8, and the operations of only the first coded packet generation unit805, the second coded packet generation unit 811, the first errordetection code added frame/packet identification number addition unit806, and the second error detection code added frame/packetidentification number addition unit 812 shown in FIG. 8 are different.Described below are the differences.

That is, in the present embodiment, the first error detection code addedframe/packet identification number addition unit 806 and the seconderror detection code added frame/packet identification number additionunit 812 operate such that the same packet identification number can beadded to the coded packet data in the same frame. The operations of theprocessing units other than those described above are the same as thoseaccording to the third embodiment.

A further preferred practical example of the embodiment is similar tothat according to the second embodiment.

(4.C) Code Conversion and Reception Apparatus

The configuration and operation of the audio code conversion andreception apparatus according to the present embodiment is substantiallythe same as those of the audio code conversion and reception apparatusaccording to the second embodiment shown in FIG. 3. In FIG. 3, thenumber M of the transmission lines is 3, but M=2 in the presentembodiment. Therefore, there is no third coded data reception unit inthe present embodiment. Furthermore, since M is 2, the procedure of theoperation of the coded data reconfiguration unit 310 is different.

The operation procedure by the coded data reconfiguration unit 310 inthe present embodiment will be explained below by referring to theflowchart shown in FIG. 10. In the series of procedures shown in FIG.10, the coded data reconfiguring process of the n-th frame is performedon a given integer n.

In step S1001, control is delayed until the time obtained by adding thepredetermined maximum delay time to the time when all coded data in then-th frame should arrive at the first packet reception buffer 301 andthe second packet reception buffer 304, and then control is passed tostep S1002.

In step S 1002, a variable a for storage of a packet number stores theminimum value of the packet number of the n-th frame, and a variable bstores the maximum value of the packet number of the n-th frame.

In step S1003, the value of the variable a is substituted for thevariable i for storage of a packet number, and the repeating process isstarted from step S1004.

In step S1004, it is determined according to the detection result of anerror and a packet loss in the first error/packet loss detection unit303 whether or not an i-th packet of the n-th frame exists and there arebit errors in the first packet reception buffer 301. When the i-thpacket in the n-th frame is received in the first packet receptionbuffer 301 and there are no errors in the data as a result of thedetermination in step S1004, control is passed to step S1005. Otherwise,control is passed to step S1006.

When control is passed to step S1005, the coded data in the n-th frameoutput by the first coded data extraction unit 302 is passed to thevariable length decoding unit (not shown in the drawings; for example,corresponding to the decoding apparatus shown in FIG. 15) as the codeddata to be decoded, and control is passed to step S1008.

When control is passed to step S1006, it is determined according to adetection result of an error and a packet loss by the seconderror/packet loss detection unit 306 whether or not there is the i-thpacket of the n-th frame and there are bit errors in the second packetreception buffer 304.

When the second packet reception buffer 304 receives the i-th packet inthe n-th frame, and there are no data errors detected as a result of thedetermination in step S1006, control is passed to step S1007. Otherwise,control is passed to step S1008.

In step S1007, the coded data in the n-th frame output by the secondcoded data extraction unit 305 is passed to the variable length decodingunit (not shown in the drawings; for example, corresponding to thedecoding apparatus shown in FIG. 15) as the coded data to be decoded,and control is passed to step S1008.

In step S1008, the variable i is incremented by 1. In step S1009, it isdetermined whether or not the variable i exceeds the value of thevariable b. If it does not exceed, the processes from step S1004 arerepeated. When the variable i exceeds the variable b, a series ofrepeated processes are finished, thereby terminating the n-th framecoded data reconfiguring process.

The operation and preferable practical example of each unit other thanthose according to the present embodiment are similar to those accordingto the third embodiment.

(4.D) Advantages

According to the above-mentioned fourth embodiment, the audio codeconversion and transmission apparatus decodes the input audio data,codes the same audio data into two pieces of coded data, and transmitsthem at predetermined or adaptively variable time intervals.

The second coded transmission means codes a packet coded by the firstcoded transmission means. The code conversion and reception apparatusselects coded data having a low compression rate and high audio qualityfrom the correctly received coded data in a packet unit, and outputs theselected data. As a result, even when a less reliable transmission linein which high burst transmission error and packet loss frequently occuris used, the probability that two pieces of coded data are transmittedwith errors can be reduced, and the outstanding degradation can beprevented from being generated in decoded audio quality aftertransmission.

Furthermore, by enhancing the compression rate of the second coded data,the increase of transmission bands during the transmission of secondcoded data can be suppressed. Additionally, depending on the status of atransmission line and the intention of an audio transmitter or an audioreceiver, the first to second coded data can be transmitted to aplurality of transmission lines having different bands, and theinfluence of an error in the transmission line can be reduced.

Additionally, the code conversion and reception apparatus can decode atleast one piece of data from the two pieces of received coded data,thereby suppressing the increase of necessary arithmetic complexity ascompared with the common audio decoding apparatus.

According to the present embodiment, the code conversion andtransmission apparatus and the code conversion and reception apparatusare combined, but they can be independently used. The first to N-th codeconverted data can be interleaved other than at time intervals.

[Fifth Mode for Carrying Out the Present Invention]

In the fifth embodiment of the present invention, the code conversionand transmission apparatus includes for an integer N of 2 or larger andan integer M of 1 or larger: a) first audio code conversion andtransmission means for inputting coded packet data and transmitting allor a part of packets using predetermined transmission means; b) (N−1)units of the 2 to N-th audio code conversion and transmission means forreplicating packets for all packet data coded by the first audio codingmeans or packet data adaptively selected depending on the characteristicof input audio data or according to a predetermined rule, andtransmitting the obtained packet data at predetermined or adaptivelyvariable time intervals using transmission means the same as ordifferent from the transmission means of the first audio code conversionand transmission means; and c) means for transmitting output of thefirst to N-th audio code conversion and transmission means to the firstto M-th transmission lines.

The code conversion and reception apparatus includes d) selection meansfor selecting at least one transmission line from M transmission lines,receiving N pieces of coded data from the selected transmission line,selecting coded packet data which is received without a transmissionerror or a loss from the packet data, and outputting the selected data.The process and the function of each means of the above-mentioned codeconversion and transmission apparatus and code conversion and receptionapparatus can be realized by the program executed by the computerforming the code conversion and transmission apparatus and codeconversion and reception apparatus.

Fifth Embodiment

For detailed explanation about the fifth mode for carrying out thepresent invention, the fifth embodiment of the present invention will beexplained referring to the drawings.

(5.A) Summary

FIG. 11 shows the fifth embodiment of the present invention. As shown inFIG. 11, the embodiment of the present invention comprises an audio datacode conversion and transmission apparatus 1200, a code conversion andreception apparatus 1220, and transmission lines 1230 for transmittingcoded data. An integer N indicates the number of pieces of coded data tobe transmitted by the code conversion and transmission apparatus, and is2 or larger. An integer M indicates the number of transmission lines fortransmitting N pieces of coded data, and is 1 or larger. The codeconversion and transmission apparatus inputs audio packet data, selectsall or a part of the data, and transmits the data to the first to M-thtransmission lines.

As shown in FIG. 11, the code conversion and transmission apparatus 1200is provided with N units of first to N-th audio code conversion andtransmission units 1202, 1204, and 1205 for transmitting data to M unitsof first to M-th transmission lines 1230. An audio data reception unit1201 receives audio packet data. A first audio code conversion andtransmission unit 1202 transmits all or a part of packets of the inputaudio packet data to the audio code conversion and reception apparatus1220.

An audio data replication unit 1203 replicates all received packet dataor a part of packet data adaptively selected depending on thecharacteristic of input audio data or according to a predetermined rule,and outputs them to second to N-th audio code conversion andtransmission units 1204 and 1205.

The second audio code conversion and transmission units 1204 and 1205transmits the replicated packets by selecting packet data of the same ordifferent number of pieces of the first audio packet data partly to theaudio code conversion and reception apparatus. The first to N-th audiostream is transmitted to the first to M-th transmission lines.

In the audio code conversion and reception apparatus 1220, a receptiontransmission line selection unit 1206 selects at least one transmissionline from M transmission lines to which the code conversion andtransmission apparatus transmits data, receives N pieces of coded datafrom the selected transmission lines, and decodes the data.

As shown in FIG. 12, the code conversion and transmission apparatus 1200comprises first to N-th coded data reception units 1207, to 1209 forreceiving the coded data transmitted from the first to N-th audio codeconversion and transmission units 1202, 1204, and 1205, and a coded datareconfiguration unit 1210.

The coded data reconfiguration unit 1210 selects data from among up to Npieces of coded data received without a transmission error or a loss bythe coded data reception units 1207 to 1209, and outputs the selecteddata.

(5.B) Code Conversion and Transmission Apparatus

FIG. 12 shows the detailed configuration of the audio code conversionand transmission apparatus according to the fifth embodiment of thepresent invention. For simplicity, the number N of pieces of coded dataoutput by the apparatus is set to 2, and the number M of units oftransmission lines for transmitting coded data is set to 2. In FIG. 12,a first audio code conversion transmission unit 1300 comprises a firsttransmitted packets selection unit 1301 for selecting adaptivelytransmitted packets based on the characteristics of an audio signal andthe status of a transmission line from among the input audio packetdata; and a first error detection code added frame/packet identificationnumber addition unit 1302 for adding an error detection code and aframe/packet identification number for detection of a transmission errorand a packet loss of output coded packet data, and outputs the firstcoded data.

In FIG. 12, a second audio code conversion and transmission unit 1310comprises a packet replication unit 1303 for replicating input audiocoded packet data, a second transmitted packets selection unit 1304 forselecting a packet adaptively transmitted to a part of packet dataadaptively selected depending on the characteristic of input audiosignal or according to a predetermined rule from the replicated audiopacket data by the number equal to or different from the number of dataselected by the first audio code conversion and transmission unit 1300,and a second error detection code added frame/packet identificationnumber addition unit 1305 for adding an error detection code and apacket identification number for detecting a transmission error and apacket loss of the coded packet data output by the second transmittedpackets selection unit 1304 by a reception apparatus. The unit outputsthe second coded data.

In the present embodiment, M is set to 2, and N is set to 2. Therefore,the first and second audio code conversion and transmission data istransmitted to the two transmission lines, respectively.

The operation of the processing unit other than that described above isthe same as that according to the fourth embodiment. A furtherpreferable concrete example of the above-mentioned embodiment is similarto that according to the second embodiment.

The configuration and operation of the audio code conversion andreception apparatus are the same as those according to the fourthembodiment.

(5.C) Advantages

According to the fifth embodiment described above, the audio codeconversion and transmission apparatus converts the same audio packetdata to two pieces of coded data, and transmits them at predetermined oradaptively variable time intervals. The first audio code conversion andtransmission unit adaptively selects input audio packet data dependingon the characteristic of input audio data or according to apredetermined rule, and transmits the data. The second audio codeconversion and transmission unit replicates all packet data or a part ofpacket data adaptively selected depending on the characteristic of inputaudio data or according to a predetermined rule, selects data by thenumber same as or different from the input data, and then transmits theselected data.

The code conversion and reception apparatus selects data without anerror or a loss from correctly received coded packet data in a packetunit, selects high quality data from the data received from twotransmission lines, and outputs the selected data. As a result, evenwhen a less reliable transmission line in which high burst transmissionerror and packet loss frequently occur is used, the probability that twopieces of coded data are transmitted with errors can be reduced, and theoutstanding degradation can be prevented from being generated in decodedaudio quality after transmission.

Furthermore, by reducing the selection number of the second coded data,the increase of transmission bands during the transmission of secondcoded data can be suppressed. Additionally, depending on the status of atransmission line and the intention of an audio transmitter or an audioreceiver, the first to second coded data can be transmitted to aplurality of transmission lines having different bands, and theinfluence of an error in the transmission line can be reduced.

Additionally, the code conversion and reception apparatus can decode atleast one piece of data from the two pieces of received coded data,thereby suppressing the increase of necessary arithmetic complexity ascompared with the common audio decoding apparatus.

According to the present embodiment, the code conversion andtransmission apparatus and the code conversion and reception apparatusare combined, but they can be independently used. The first to N-th codeconverted data can be interleaved other than at time intervals.

[Sixth Mode for Carrying Out the Present Invention]

According to the sixth embodiment of the present invention, the codeconversion and transmission apparatus includes for an integer N of 2 orlarger and an integer M of 1 or larger: a) first audio code conversionand transmission means for inputting compressed coded data, decoding theinput coded data, compressing and coding the data at a compression rateequal to or higher than the rate of the input coded data, andtransmitting all frames or a frame adaptively selected depending on thecharacteristic of input audio data or according to a predetermined ruleusing predetermined transmission means; b) (N−1) units of the second toN-th audio code conversion and transmission means for decoding inputcoded data, compressing and coding data at a compression rate equal toor higher than the rate of the first audio code conversion andtransmission means, and transmitting all frames of the obtained codeddata or a part of frames adaptively selected depending on thecharacteristic of input audio data or according to a predetermined ruleat predetermined or adaptively variable time intervals usingtransmission means the same as or different from the transmission meansof the first audio code conversion and transmission means; and c) meansfor selecting a compression rate of the first to N-th audio codeconversion and transmission means depending on the band available foreach of the first to M transmission lines, and transmitting the selectedresult to the first to M-th transmission lines.

The code conversion and reception apparatus includes d) selection meansfor selecting at least one transmission line from M transmission lines,receiving N pieces of coded data from the selected transmission line,extracting coded data received without a transmission error or a loss,selecting audio coded data having the lowest compression rate from thecoded data in the same frame, and outputting the selected data. Theprocess and function of each means of the above-mentioned codeconversion and transmission apparatus and code conversion and receptionapparatus can be realized by the program executed by the computerconfiguring the above-mentioned code conversion and transmissionapparatus and code conversion and reception apparatus.

Sixth Embodiment

For detailed explanation about the sixth mode for carrying out thepresent invention, the sixth embodiment of the present invention will beexplained referring to the drawings.

(6.A) Summary

FIG. 13 shows the sixth embodiment of the present invention. As shown inFIG. 13, the embodiment of the present invention comprises an audio datacode conversion and transmission apparatus 1400, a code conversion andreception apparatus 1420, and transmission lines 1430 for transmittingcoded data. An integer N indicates the number of pieces of coded data tobe transmitted by the code conversion and transmission apparatus, and is2 or larger. An integer M indicates the number of transmission lines fortransmitting N pieces of coded data, and is 1 or larger.

The audio code conversion and transmission apparatus 1400 decodes inputcoded audio data, and the obtained audio data is compressed and coded ina predetermined method at a compression rate equal to or higher than therate of the input data, and transmitted to the audio code conversion andreception apparatus 1420. The input audio data is coded into N pieces ofcoded data, and transmitted to the first to M-th transmission lines asthe first to N-th audio coded data.

As shown in FIG. 13, the audio code conversion and transmissionapparatus comprises N units of first to N-th audio code conversion andtransmission units (the first to N-th audio code conversion andtransmission unit) 1403, 1404, and 1405.

An audio data reception unit 1401 receives audio data.

An audio data decoding unit 1402 decodes input audio coded data.

A first audio code conversion and transmission unit 1403 compresses andcodes a frame input to the code conversion and transmission apparatus ina predetermined method, and transmits the obtained coded data to theaudio code conversion and reception apparatus.

Second to N-th audio code conversion and transmission units 1404 and1405 code data at a compression rate equal to or higher than the rate ofthe first audio code conversion and transmission unit 1403, andtransmits the obtained coded data to the audio code conversion andreception apparatus. The first to N-th audio stream is transmitted tothe first to M-th transmission lines.

In the present embodiment, the compression rate for coding by the firstto N-th audio code conversion and transmission unit 1403 to 1405 can beselected depending on the band available for transmission of audio databy each transmission line 1430. The output of the first to N-th audiocode conversion and transmission units 1403 to 1405 is output to thefirst to M-th transmission lines 1430, thereby transmitting datadepending on the status of the transmission line and the intention ofthe transmitter of audio data.

In the audio code conversion and reception apparatus 1420, a receptiontransmission line selection unit 1406 selects at least one transmissionline from among the M transmission lines used by the audio codeconversion and transmission apparatus for transmission, receives Npieces of coded data from the selected transmission line, and decodesthe received data.

As shown in FIG. 13, the audio code conversion and reception apparatus1420 comprises first to N-th coded data reception units 1407 to 1409 forreceiving the coded data transmitted by the first to N-th audio codeconversion and transmission units 1403 to 1405 of the code conversionand transmission apparatus 1400, and a coded data reconfiguration unit1410.

The coded data reconfiguration unit 1410 selects the data having thelowest compression rate from among up to N pieces of coded data receivedwithout a transmission error or a loss by the coded data reception units1407 to 1409 and outputs the selected data.

(6.B) Code Conversion and Transmission Apparatus

FIG. 14 shows the detailed configuration of the audio code conversionand transmission apparatus according to the sixth embodiment of thepresent invention. For simplicity, the number N of pieces of coded dataoutput by the apparatus is set to 2, and the number M of units oftransmission lines for transmitting coded data is set to 2. In FIG. 14,the apparatus comprises a decoding unit 1501 for decoding input audiodata, and a first audio code conversion and transmission unit 1500comprises a first transmitted frame/packet coding unit 1502 for codingdecoded audio data at a compression rate equal to or higher than therate of the input data, and a first error detection code addedframe/packet identification number addition unit 1503 for adding anerror detection code and a frame/packet identification number fordetecting by the reception apparatus a transmission error and a packetloss of the coded data output by the first transmission frame/packetcoded unit 1502, outputs the first audio coded data, and transmits thedata by predetermined transmission means.

In FIG. 14, a second audio code conversion and transmission unit 1510comprises a second transmitted frame/packet coding unit 1504 for codingdata at a compression rate equal to or higher than the rate of the firstaudio code conversion and transmission unit 1500 and outputting thecoded data, and a second error detection code added frame/packetidentification number addition unit 1505 for adding an error detectioncode and frame/packet identification number for detection of atransmission error and a packet loss of the coded data output by thesecond transmission frame/packet coded unit 1504 by a receivingapparatus, and the second audio coded data is output and transmitted bypredetermined transmission means.

In the present embodiment, M is set to 2, and N is set to 2. Therefore,the first to second audio code conversion and transmission data istransmitted to each of the two transmission lines. The operation of theprocessing unit other than the above-mentioned operation is similar tothat according to the third embodiment.

A further preferable concrete example of the above-mentioned embodimentis similar to that according to the first embodiment.

The configuration and operation of the audio code conversion andreception apparatus are the same as those according to the thirdembodiment.

(6.C) Advantages

According to the third embodiment described above, the audio codeconversion and transmission apparatus decodes input audio data, codesthe same audio data into two pieces of coded data, and transmits thecoded data at predetermined or adaptively variable time intervals.

The code conversion and reception apparatus selects coded data having alow compression rate and high audio quality from the correctly receivedcoded data in a frame unit, and outputs the selected data. As a result,even when a less reliable transmission line in which high bursttransmission error and packet loss frequently occur is used, theprobability that two pieces of coded data are transmitted with errorscan be reduced, and the outstanding degradation can be prevented frombeing generated in decoded audio quality after transmission.

Furthermore, by enhancing the compression rate of the second coded data,the increase of transmission bands during the transmission of secondcoded data can be suppressed.

Additionally, depending on the status of a transmission line and theintention of an audio transmitter or an audio receiver, the first tosecond coded data can be transmitted to a plurality of transmissionlines having different bands, and the influence of an error in thetransmission line can be reduced. Additionally, the code conversion andreception apparatus can decode at least one piece of data from the twopieces of received coded data, thereby suppressing the increase ofnecessary arithmetic complexity as compared with the common audiodecoding apparatus.

According to the present embodiment, the code conversion andtransmission apparatus and the code conversion and reception apparatusare combined, but they can be independently used. The first to N-th codeconverted data can be interleaved other than at time intervals.

[Seventh Mode for Carrying Out the Present Invention]

In the seventh embodiment of the present invention, the code conversionand transmission apparatus includes for an integer N of 2 or larger andan integer M of 1 or larger: a) first audio code conversion andtransmission means for inputting compressed coded packet data, decodingthe input coded packet data, compressing and coding data at acompression rate equal to or higher than the rate of the input codeddata, and transmitting all packets or a part of packets adaptivelyselected depending on the characteristic of input audio data oraccording to a predetermined rule using predetermined transmissionmeans; b) (N−1) units of the second to N-th audio code conversion andtransmission means for decoding input coded packet data, compressing andcoding data into packet data at a compression rate equal to or higherthan the rate of the first audio code conversion and transmission means;and transmitting all obtained packet data or a part of packet dataadaptively selected depending on the characteristic of input audio dataor according to a predetermined rule at predetermined or adaptivelyvariable time intervals using transmission means the same as ordifferent from the transmission means of the first audio code conversionand transmission means; and c) means for selecting compression rate forthe first to N-th audio code conversion and transmission means dependingon the band available for each of the first to M-th transmission lines,and transmitting it to the first to M-th transmission lines.

The code conversion and reception apparatus includes d) selection meansfor selecting at least one transmission line from M transmission lines,receiving N pieces of coded data from the selected transmission line,selecting coded packet data which has the lowest compression rate fromthe packet data received without a transmission error or a loss, andoutputting the selected data. The process and function of each means ofthe above-mentioned code conversion and transmission apparatus and codeconversion and reception apparatus can be realized by the programexecuted by the computer configuring the above-mentioned code conversionand transmission apparatus and code conversion and reception apparatus.

Seventh Embodiment

For detailed explanation about the seventh mode for carrying out thepresent invention, the seventh embodiment of the present invention willbe explained referring to the drawings.

(7.A) Summary

The configuration and operation of the present embodiment aresubstantially the same as those according to the sixth embodiment. Asshown in FIG. 13, the embodiment of the present invention comprises theaudio code conversion and transmission apparatus 1400, the codeconversion and reception apparatus 1420, and the transmission lines 1430for transmitting coded data. An integer N indicates the number of piecesof coded data to be transmitted by the code conversion and transmissionapparatus, and is 2 or larger. An integer M indicates the number oftransmission lines for transmitting N pieces of coded data, and is 1 orlarger.

The configuration of the audio code conversion and transmissionapparatus is substantially the same as that according to the sixthembodiment, but the operation of each unit configuring the apparatus issomewhat different. Described below are the differences.

The input audio coded data is decoded, data is compressed and coded in apredetermined method at a compression rate equal to or higher than therate of the input audio data, and the code converted data is transmittedto the audio code conversion and reception apparatus.

The input frame coded data coded by the audio image code conversionprocessing unit is configured by one or more pieces of packet data.

The second to N-th audio code conversion and transmission units codesall or a part of packets coded by the first audio code conversion andtransmission unit at a compression rate equal to or higher than the rateof the first audio code conversion and transmission unit, and theobtained coded packet data is transmitted to the audio code conversionand reception apparatus. The operations other than those described aboveare basically the same as in the sixth embodiment.

The configuration of the audio code conversion and reception apparatusis also substantially the same as that according to the sixthembodiment, but the operation of each unit configuring the apparatus issomewhat different. Described below are the differences.

In FIG. 13, the coded data reconfiguration unit 1410 selects a packethaving the lowest compression rate as coded data to be decoded fromamong up to N pieces of coded packet data which are received without atransmission error or a loss by the first to N-th coded data receptionunits, and include compressed data in the same frame, and the selectionresult is transmitted by the code conversion and transmission apparatusin a packet unit as in the sixth embodiment. The operations other thanthe operations above are basically the same as in the sixth embodiment.

(7.B) Code Conversion and Transmission Apparatus

The configuration and operation of the audio data code conversion andtransmission apparatus according to the present embodiment aresubstantially the same as those of the audio data code conversion andtransmission apparatus according to the sixth embodiment shown in FIG.14, and the operations of only the first transmitted frame/packet codingunit 1502, the second transmitted frame/packet coding unit 1504, thefirst error detection code added frame/packet identification numberaddition unit 1503, and the second error detection code addedframe/packet identification number addition unit 1505 shown in FIG. 14are different. Described below are the differences.

In the audio data code conversion and transmission apparatus accordingto the present embodiment, the first transmitted frame/packet codingunit 1502 and the second transmitted frame/packet coding unit 1504generate coded packet data such that the frame of the coded packet datagenerated by the first transmitted frame/packet coding unit 1502 canmatch the frame of the coded packet data generated by the secondtransmitted frame/packet coding unit 1504. The operations of the unitsother than those described above are similar to those according to thesixth embodiment.

A further preferred practical example of the embodiment is similar tothat according to the second embodiment. The configuration and operationof the audio code conversion and reception apparatus are the same asthose according to the fourth embodiment.

(7.C) Advantages

According to the above-mentioned seventh embodiment, the audio codeconversion and transmission apparatus decodes the input audio data,codes the same audio data into two pieces of coded data, and transmitsthem at predetermined or adaptively variable time intervals. The secondcoded transmission means codes a packet coded by the first codedtransmission means.

The code conversion and reception apparatus selects coded data having alow compression rate and high audio quality from the correctly receivedcoded data in a packet unit, and outputs the selected data. As a result,even when a less reliable transmission line in which high bursttransmission error and packet loss frequently occur is used, theprobability that two pieces of coded data are transmitted with errorscan be reduced, and the outstanding degradation can be prevented frombeing generated in decoded audio quality after transmission.

Furthermore, by enhancing the compression rate of the second coded data,the increase of transmission bands during the transmission of secondcoded data can be suppressed. Additionally, depending on the status of atransmission line and the intention of an audio transmitter or an audioreceiver, the first to second coded data can be transmitted to aplurality of transmission lines having different bands, and theinfluence of an error in the transmission line can be reduced.

Additionally, the code conversion and reception apparatus can decode atleast one piece of data from the two pieces of received coded data,thereby suppressing the increase of necessary arithmetic complexity ascompared with the common audio decoding apparatus.

According to the present embodiment, the code conversion andtransmission apparatus and the code conversion and reception apparatusare combined, but they can be independently used. The first to N-th codeconverted data can be interleaved other than at time intervals.

[Eighth Mode for Carrying Out the Present Invention]

Described below is another embodiment of the present invention. FIG. 15shows the system configuration of the eighth embodiment of the presentinvention. In FIG. 15, the system comprises a coding apparatus 40 foroutputting coded data, an audio data code conversion and transmissionapparatus 10, code conversion and reception apparatuses 20_1_ to 20_K_for a plurality of (K) audio data, and a plurality of (K) decodingapparatuses 30 ₁ to 30 _(K) connected to the code conversion andreception apparatuses 20 ₁ to 20 _(K). The coding apparatus 40 forms aninformation providing source for distributing coded data, and awell-known server apparatus is used as the apparatus. The codeconversion and transmission apparatus 10 comprises the code conversionand transmission apparatus (for example, 100 shown in FIG. 1) accordingto the present invention as explained above in the above-mentioned firstto ninth embodiments.

The plurality of audio data code conversion and reception apparatuses 20comprise a code conversion and reception apparatus (for example, 120shown in FIG. 1) according to the present invention as explained abovein the above-mentioned first to ninth embodiments. The decodingapparatus 30 is an apparatus (decoder) for decoding and displaying thecoded data from the code conversion and reception apparatus 20. Aready-made product can be used.

In the example shown in FIG. 15, one transmission line 13 used intransferring information between the code conversion and transmissionapparatus 10 and each of the code conversion and reception apparatuses20 ₁ to 20 _(K) is assigned to each code conversion and receptionapparatus. That is, in the M transmission lines 130 in the example ofFIG. 1, M is assumed to be 1, and there is provided a plurality of codeconversion and reception apparatuses 120 in FIG. 1. The code conversionand transmission apparatus 10 is provided with N audio code conversionand transmission units, not shown in the drawings, and N pieces ofstream data are output as in each of the above-mentioned embodiments.

As an embodiment of the practical example of the present embodiment ofthe present invention, the code conversion and transmission apparatus 10is connected to the Internet communications network (or Intranet), andinputs coded data transmitted using the UDP/IP protocol from the codingapparatus 40. The process of the audio code conversion and transmissionunit, not shown in the drawings, of the code conversion and transmissionapparatus 10 is performed corresponding to, for example, Real-timeTransport Protocol (RTP). The code conversion and reception apparatus 20can be a client terminal connected to, for example, the Internetcommunications network.

In the embodiment, when the transmission line is wireless, the codeconversion output (N stream data) from the code conversion andtransmission apparatus 10 is output through an UDP/IP protocol and aphysical layer, and to the destination code conversion and receptionapparatus 20 through the base station in the mobile packetcommunications system network through a router and a gateway, etc. Inthe code conversion and reception apparatus 20, the data code-convertedby the code conversion and transmission apparatus 10 between the codingapparatus 40 and the decoding apparatus 30 is reconfigured into codeddata corresponding to the original coding of the coding apparatus 40,and the obtained data is output. The decoding apparatus 30 outputs audiodata to the audio output apparatus, not shown in the drawings, byperforming a decoding process corresponding to the coding by the codingapparatus 40. The decoding apparatus (decoder) 30 connected to the codeconversion and reception apparatus 20 can be configured as a terminalincorporated into the code conversion and reception apparatus 20, or canbe provided for a terminal (personal computer), etc. connected forcommunications with a terminal configuring the code conversion andreception apparatus 20.

In the embodiment, the code conversion and reception apparatus 20outputs a control signal (request signal) to the code conversion andtransmission apparatus 10. The code conversion and transmissionapparatus 10 receives the control signal, and transmits coded data tothe code conversion and reception apparatus 20. FIG. 15 indicates thatthe control signal is different from the coded stream output from thecode conversion and transmission apparatus 10.

Using the control signal transmitted from the code conversion andreception apparatus 20 to the code conversion and transmission apparatus10, the system information about the code conversion and receptionapparatus 20, for example, an IP address, apparatus information, thecoding system available by the decoding apparatus 30 (for example, H.261or H.263 recommended by ITU-T, MPEG-4 Visual recommended by ISO/IEC),etc. can be provided through the code conversion and transmissionapparatus 10 so that the code conversion and transmission apparatus 10which receives a request signal can perform the code conversion appliedto the code conversion and reception apparatus 20 and decoding apparatus30. According to the present invention, it is obvious that thetransmission line can be a cable.

In the configuration shown in FIG. 15, the coded stream data of aplurality of lines (N) output to the transmission lines 13,respectively, from the code conversion and transmission apparatus 10 canbe multiplexed by a multiplexer at different time intervals by the delayaddition unit as shown in FIG. 5, or N streams of data can beinterleaved by the multiplexing unit and the transmission order can berearranged by the shuffling, thereby transmitting multiplexed output atintervals through a transmission line. It is also possible to providethe delay addition unit and multiplexer as shown in FIG. 5 in the codeconversion and transmission apparatus 10. In this case, the codeconversion and reception apparatus 20 comprises a separation unit 511shown in FIG. 5, and the multiplexing transmission packet received bythe transmission line selected by the reception transmission lineselection unit is separated into a packet of each stream, and theextraction and reconfiguration of coded data are performed. In thisembodiment, the coded data from the coding apparatus 40 functioning asan information provider is received by the code conversion andtransmission apparatus 10. The code conversion and transmissionapparatus 10 performs the conversion for protection against a data lossand data error, transmits data to the code conversion and receptionapparatus 20, and coded data can be efficiently transmitted through thetransmission line 13. The decoding apparatus 30 performs decodingcorresponding to the coding method of the coding apparatus 40.

While the present invention has been described with reference to theparticular illustrative embodiments, it is not to be restricted by theembodiments but only by the appended claims. It is to be appreciatedthat those skilled in the art can change or modify the embodimentswithout departing from the scope and spirit of the present invention.

INDUSTRIAL APPLICABILITY

As explained above, according to the present invention, even when a lessreliable transmission line in which high burst transmission error andpacket loss frequently occur is used, the probability that N pieces ofcoded data are transmitted with errors can be reduced, and theoutstanding degradation can be prevented from being generated in decodedaudio quality. The reasons will be described below.

That is, according to the present invention, relating to the integer Nwhich is two or larger, and the integer M which is 1 or larger, the codeconversion and transmission apparatus comprises the first to N-th audiocode conversion and transmission means on the first to M-th transmissionlines, and all or a part of the frames or a packets of audio data istransmitted, or after decoding, the audio data is compressed and codedinto N pieces of the coded data and transmitted at predetermined oradaptively variable time intervals. The second to N-th audio codeconversion and transmission means codes input frames, and the codeconversion and reception apparatus selects the coded data having thelowest compression rate and enhanced audio quality from correctlyreceived coded data from the M transmission lines in a frame or a packetunit, and then decoded.

According to the present invention, the status of a transmission line orthe transmission based on the intention of audio data transmitter can bereflected in the transmission.

The reason is that, according to the present invention, using the firstto M-th transmission lines, the compression rate of the first to N-thaudio code conversion and transmission means can be selected dependingon the band available in the transmission of audio data in eachtransmission line.

Furthermore, according to the present invention, the increase oftransmission rate by a plurality of coded data transmission processescan be reduced.

Since, according to the present invention, second to N-th audio codeconversion and transmission means codes data at a compression rate equalto or higher than the rate of the first audio code conversion andtransmission means. The transmission of coded data by the second to N-thaudio code conversion and transmission means can be performed only onthe frame coded by the first audio code conversion and transmissionmeans.

Furthermore, according to the present invention, the increase ofarithmetic complexity, which is required by a receiver, can be reduced.

The reason is that the code conversion and transmission apparatusgenerates coded data including the same frames, and the code conversionand reception apparatus selects and decodes only one piece of data in aframe or a packet unit from plural pieces of received coded data.Therefore, it is not necessary for the code conversion and receptionapparatus to decode plural pieces of received coded data.

1. An audio data code conversion and reception apparatus, comprising:selection means for selecting a transmission line for receiving codeddata from among first to M-th (M is a predetermined integer equal to 1or larger) transmission lines; and means for receiving coded data from atransmission line selected by said selection means, extracting codeddata received without a transmission error or a loss, and reconfiguringand outputting coded data based on extracted coded data.
 2. An audiodata code conversion and reception apparatus, comprising: selectionmeans for selecting a transmission line for receiving coded data fromamong first to M-th (M is a predetermined integer equal to 1 or larger)transmission lines; and means for receiving coded data from atransmission line selected by said selection means, extracting codedpacket data received without a transmission error or a loss, andreconfiguring and outputting coded packet data based on extracted codedpacket data.
 3. The audio data code conversion and reception apparatusaccording to claim 1, characterized in that said apparatus furthercomprises means for selecting one piece of data based on a compressionrate from coded data in a same frame received from the selectedtransmission line.
 4. The audio data code conversion and receptionapparatus according to claim 2, characterized in that said apparatusfurther comprises means for selecting one piece of data based on acompression rate from packet data in a same frame received from theselected transmission line.
 5. An audio data code conversion andreception method, comprising: a step of selecting a transmission linefor receiving coded data from among first to M-th (M is a predeterminedinteger equal to 1 or larger) transmission lines; and a step ofreceiving coded data from the selected transmission line, extractingaudio coded data received without a transmission error or a loss, andreconfiguring and outputting audio coded data based on extracted codeddata.
 6. An audio data code conversion and reception method, comprising:a step of selecting a transmission line for receiving coded packet datafrom among first to M-th (M is a predetermined integer equal to 1 orlarger) transmission lines; and a step of receiving audio coded packetdata from the selected transmission line, extracting coded packet datareceived without a transmission error or a loss, and reconfiguring andoutputting audio coded packet data based on extracted coded packet data.7. The audio data code conversion and reception method according toclaim 5, characterized in that one piece of data is selected based on acompression rate from coded data in a same frame received from theselected transmission line.
 8. The audio data code conversion andreception method according to claim 6, characterized in that one pieceof data is selected based on a compression rate from packet data in asame frame received from the selected transmission line.
 9. The audiodata code conversion and transmission method, comprising: a step offirst audio code conversion and transmission means inputting compressedaudio coded data, and outputting all or a part of frames of the inputaudio coded data; a step of second to N-th (N is a predetermined integerequal to or larger than 2) audio code conversion and transmission meansdecoding all or a part of input audio coded data, coding data obtainedby decoding data, and outputting all or a part of frames of obtainedcoded data; a step of means transmitting output of the first to N-thaudio code conversion and transmission means to first to M-th (M is apredetermined integer equal to or larger than 1) transmission lines; astep of selecting a transmission line for receiving coded data fromamong first to M-th (M is a predetermined integer equal to 1 or larger)transmission lines; and a step of receiving coded data from the selectedtransmission line, extracting audio coded data received without atransmission error or a loss, and reconfiguring and outputting audiocoded data based on extracted coded data.
 10. The audio data codeconversion and transmission method comprising: a step of first audiocode conversion and transmission means inputting compressed audio codedpacket data and outputting all or a part of packets of the input audiocoded data; a step of second to N-th (N is a predetermined integer equalto or larger than 2) audio code conversion and transmission meansdecoding the input audio coded packet data, coding data obtained bydecoding data, and outputting all or a part of obtained packet data; astep of means transmitting output of the first to N-th audio codeconversion and transmission means to first to M-th (M is a predeterminedinteger equal to or larger than 1) transmission lines; a step ofselecting a transmission line for receiving coded data from among firstto M-th (M is a predetermined integer equal to 1 or larger) transmissionlines; and a step of receiving coded data from the selected transmissionline, extracting audio coded data received without a transmission erroror a loss, and reconfiguring and outputting audio coded data based onextracted coded data.
 11. The audio data code conversion andtransmission method comprising: a step of first audio code conversionand transmission means inputting compressed audio coded data, decodingthe input audio coded data, coding data obtained by decoding, andoutputting all or a part of obtained frames; a step of second to N-th (Nis a predetermined integer equal to 2 or larger) audio code conversionand transmission means decoding the input audio coded data, coding dataobtained by decoding, and outputting all or a part of obtained frames ofcoded data; a step of means transmitting output of the first to N-thaudio code conversion and transmission means to first to M-th (M is apredetermined integer equal to 1 or larger) transmission lines; a stepof selecting a transmission line for receiving coded data from amongfirst to M-th (M is a predetermined integer equal to 1 or larger)transmission lines; and a step of receiving coded data from the selectedtransmission line, extracting audio coded data received without atransmission error or a loss, and reconfiguring and outputting audiocoded data based on extracted coded data.
 12. The audio data codeconversion and transmission method comprising: a step of first audiocode conversion and transmission means inputting compressed audio codeddata, and outputting all or a part of frames; a step of second to N-th(N is a predetermined integer equal to 2 or larger) audio codeconversion and transmission means decoding the input audio coded data,coding data obtained by decoding, and outputting all or a part of framesof coded data obtained by coding; a step of means transmitting output ofthe first to N-th audio code conversion and transmission means to firstto M-th (M is a predetermined integer equal to 1 or larger) transmissionlines; a step of selecting a transmission line for receiving coded datafrom among first to M-th (M is a predetermined integer equal to 1 orlarger) transmission lines; and a step of receiving coded data from theselected transmission line, extracting audio coded data received withouta transmission error or a loss, and reconfiguring and outputting audiocoded data based on extracted coded data.
 13. The audio data codeconversion and reception method according to claim 9, characterized inthat one piece of data is selected based on a compression rate fromcoded data in a same frame received from the selected transmission line.14. The audio data code conversion and reception method according toclaim 10, characterized in that one piece of data is selected based on acompression rate from coded data in a same frame received from theselected transmission line.
 15. The audio data code conversion andreception method according to claim 11, characterized in that one pieceof data is selected based on a compression rate from coded data in asame frame received from the selected transmission line.
 16. The audiodata code conversion and reception method according to claim 12,characterized in that one piece of data is selected based on acompression rate from coded data in a same frame received from theselected transmission line.
 17. The audio data code conversion andtransmission method, comprising: a step of first audio code conversionand transmission means inputting compressed audio coded packet data andoutputting all or a part of packets of the input audio coded data; astep of second to N-th (N is a predetermined integer equal to or largerthan 2) audio code conversion and transmission means decoding the inputaudio coded packet data, coding data obtained by decoding data, andoutputting all or a part of obtained packet data; a step of meanstransmitting output of the first to N-th audio code conversion andtransmission means to first to M-th (M is a predetermined integer equalto or larger than 1) transmission lines; a step of selecting atransmission line for receiving coded packet data from among first toM-th (M is a predetermined integer equal to 1 or larger) transmissionlines; and a step of receiving audio coded packet data from the selectedtransmission line, extracting coded packet data received without atransmission error or a loss, and reconfiguring and outputting audiocoded packet data based on extracted coded packet data.
 18. The audiodata code conversion and transmission method, comprising: a step offirst audio code conversion and transmission means inputting compressedaudio coded packet data, coding data obtained by decoding the inputaudio coded packet data, and outputting obtained coded packet data; astep of second to N-th (N is a predetermined integer equal to 2 orlarger) audio code conversion and transmission means coding all or apart of packet data coded by said first audio code conversion andtransmission means, coding packet data obtained by decoding andoutputting obtained coded packet data; a step of means transmittingoutput of the first to N-th audio code conversion and transmission meansto first to M-th (M is a predetermined integer equal to 1 or larger)transmission lines; a step of selecting a transmission line forreceiving coded packet data from among first to M-th (M is apredetermined integer equal to 1 or larger) transmission lines; and astep of receiving audio coded packet data from the selected transmissionline, extracting coded packet data received without a transmission erroror a loss, and reconfiguring and outputting audio coded packet databased on extracted coded packet data.
 19. The audio data code conversionand transmission method, comprising: a step of first audio codeconversion and transmission means inputting compressed audio codedpacket data, and outputting all or a part of all or a part of the inputaudio coded packet data; a step of second to N-th (N is a predeterminedinteger equal to 2 or larger) audio code conversion and transmissionmeans replicating a packet for all or a part of packet data of audiocoded packet data input to said first audio code conversion andtransmission means, and outputting the packet data obtained byreplication; a step of means transmitting output of the first to N-thaudio code conversion and transmission means to first to M-th (M is apredetermined integer equal to 1 or larger) transmission lines; a stepof selecting a transmission line for receiving coded packet data fromamong first to M-th (M is a predetermined integer equal to 1 or larger)transmission lines; and a step of receiving audio coded packet data fromthe selected transmission line, extracting coded packet data receivedwithout a transmission error or a loss, and reconfiguring and outputtingaudio coded packet data based on extracted coded packet data.
 20. Theaudio data code conversion and transmission method, comprising: a stepof first audio code conversion and transmission means inputtingcompressed audio coded packet data, decoding the input coded packetdata, coding packet data obtained by decoding, and outputting all or apart of packets obtained by coding; a step of second to N-th (N is apredetermined integer equal to 2 or larger) audio code conversion andtransmission means decoding input coded packet data, coding packet dataobtained by decoding, and outputting all or a part of packet dataobtained by coding; a step of means transmitting output of the first toN-th audio code conversion and transmission means to first to M-th (M isa predetermined integer equal to 1 or larger) transmission lines; a stepof selecting a transmission line for receiving coded packet data fromamong first to M-th (M is a predetermined integer equal to 1 or larger)transmission lines; and a step of receiving audio coded packet data fromthe selected transmission line, extracting coded packet data receivedwithout a transmission error or a loss, and reconfiguring and outputtingaudio coded packet data based on extracted coded packet data.
 21. Theaudio data code conversion and reception method according to claim 17,characterized in that one piece of data is selected based on acompression rate from packet data in a same frame received from theselected transmission line.
 22. The audio data code conversion andreception method according to claim 18, characterized in that one pieceof data is selected based on a compression rate from packet data in asame frame received from the selected transmission line.
 23. The audiodata code conversion and reception method according to claim 19,characterized in that one piece of data is selected based on acompression rate from packet data in a same frame received from theselected transmission line.
 24. The audio data code conversion andreception method according to claim 20, characterized in that one pieceof data is selected based on a compression rate from packet data in asame frame received from the selected transmission line.
 25. A programused to direct a computer configuring an audio data code conversion andtransmission apparatus to perform a code conversion and transmissionprocess on audio coded data, comprising: a process of selecting at leastone transmission line from among M (M is a predetermined integer equalto 1 or larger) transmission lines; and a process of receiving audiocoded data from the selected transmission line, extracting coded datareceived without a transmission error or a loss, and reconfiguring andoutputting audio coded data based on the extracted coded data.
 26. Aprogram used to direct a computer configuring an audio data codeconversion and transmission apparatus to perform a code conversion andtransmission process on audio coded data, comprising: a process ofselecting at least one transmission line from among M (M is apredetermined integer equal to 1 or larger) transmission lines; and aprocess of receiving audio coded data from the selected transmissionline, extracting packet data received without a transmission error or aloss, and reconfiguring and outputting audio coded data based on theextracted packet data.
 27. The program according to claim 25, used todirect a computer to perform a process of selecting audio coded databased on a compression rate and outputting the selected audio coded datawhen there are plural pieces of audio coded data in a same framereceived from the selected transmission line.
 28. The program accordingto claim 26, used to direct a computer to perform a process of selectingaudio coded packet data based on a compression rate and reconfiguringand outputting the audio coded data when there are plural pieces ofcoded packet data in a same frame received from the selectedtransmission line.